There is no "best", only what works with the highest efficiency into your loudspeaker load and which suits your situation overall.
I cannot speak directly to the issue of the 110's, however, this generation of B&W products were known to be rather unfriendly towards amplifiers.
They have rather severe impedance and electrical phase issues which made them difficult to drive with anything less than the stoutest of amplifiers.
Stout amplifiers are not commonly seen in receivers due to the nature of how a compromise product such as a receiver is designed. In general, AV receivers with multiple channels of output are even less capable when faced with the difficult load of the average B&W speaker. A typical problem with lower quality amplifiers and the B&W speakers from this time would have been overheating of the amplifier and shutting down of the system. To avoid this problem, you either need to keep your volume requirements very modest or you need to buy a higher quality amplifier more suited to the electrical requirements of the loudspeakers.
Very briefly, when impedance and phase are an issue, flat frequency response and signal coherence are sacrificed unless the load is paired with a very "high current capable" amplifier.
There are, of course, other impediments to flat frequency response and coherence with any multiple speaker set up. If though, the amplifier is not up to the task of adequately driving the loudspeaker, you are starting out behind the eight ball.
If you are looking for the best two channel music reproduction from any amplifier mated with the B&W's, I would suggest you look for a line which advertises (and traditionally delivers) high current capacity.
Harman Kardon is such a line.
There are others but HK has long been recognized as building power amplifiers known for high and sustained current delivery into difficult loads.
Wattage alone is largely irrelevant in an AV receiver for multiple reasons.
Read that sentence again.
Current delivery is a function of supplying "amperage" to the speaker load on a continuous basis and, when required, very high amperage to deal with dynamic spikes in volume level and/or very low impedance dips in impedance and/or high swings in electrical phase angle. The B&W line was known for combining both low impedance and high phase angle at similar frequencies which makes for trouble when it comes to an amplifier.
The diversity in how to build and measure an AV receiver makes selecting based only on wattage a fool's game.
Read that sentence again.
If I had to give one piece of overall advice for anyone using this generation of B&W loudspeakers, it would be to buy the heaviest (by weight) amplifier you can afford.
Certainly, if two receivers are more or less equal in stated wattage, buy the amplifier which weighs the most. That weight is coming from a "better", more capable power supply.
It's the power supply that matters first and foremost in an amplifier, even more so when it must drive a difficult load.
I want to elaborate on something Jan said about amplifiers and B&W in particular. First, 10 watts is an almost immeasurable difference when applied to a real speaker. It WOULD matter if the first amp were 10 watts and the 2nd measured 20 watts. But the difference between 90 watts and 100 watts? Amp TEST LOADS consist almost exclusively of a simple resistor. Exceptions to this exist, but are generally NOT advertised when doing amp power measures. A resistor is Very Good at turning electricity into heat. As it turns out, you can have 2 amps which are your 10 watts apart INTO A RESISTIVE LOAD while measureing the exact opposite into a real speaker load. Speakers look like, at various frequencies, either a capacitor or an inductor. Amplifiers vary more in the ability to work into those loads than the simple resistor test favored by spec-nuts.
As for 'buy the heaviest amplifier you can afford'. In general good advice. The exceptions, however are legion. A class of amplifier called 'd' amps generally use a power supply which does NOT have a large, heavy, transformer. And the output devices, the LAST electronics the signal sees before getting to the speakers, are being mounted on large, heavy 'heat sinks' is ALSO not the case for 'd' amps. Heatsinks and Power Supply are the 2 major sources of warmth / heat from MOST amplifiers, though Home Theater stuff is so crowded in the case that the WHOLE THING is simply cooking itself. Amps of the 'd' persuasion are generally much lighter and cooler running for ANY given power output. And can be as capable as more traditional amps in driving 'odd' loads or even those B&Ws.
Some HT receivers have adopted 'd' amps in an effort to reduce weight and heat. One company I know recently stopped production of a 100lb amplifier because of shipping damage. Too Many were getting broken by shippers, even AFTER being strapped to a Pallet to make it worthwhile. Besides, to get that amp (you needed 2, it was mono) to FIT in your system required some HELP from probably drunken friends.
My opinion? If your receiver has PRE AMP OUTPUTS, and you otherwise like it, would be to buy a good external amplifier. EMOTIVA is currently selling a 200x5 amp for 800$ on closeout. A decent and well regarded amp. Emotiva is ALSO going to 'd' amps for some of its line, using amps manufactured by one of the 'biggies' and doing a repackage. But that'll cost 50% more. At least.
The difference in volume capacity (or SPL's [sound pressure levels]) is very minimal whenever you double the available wattage.
That first assumes all things are equal between the two amplifiers. Probably, between two Marantz receivers, that's a safe bet. Between two different manufacturer's lines, there's no guarantee of similar amplifier quality.
Technically, if you double the available wattage into the same "ideal" loudspeaker load, you will only gain 3 decibels in total volume potential. "Total volume potential" means the extra volume will exist at the loudest signal levels only.
In other words, by doubling the rated wattage, the higher powered amp will be ever so slightly less likely to "clip" or distort the loudest sounds. The average sounds will remain "average". You will typically need 10 ttimes as much wattage to actually notice the aamp can play louder with the same lloudspeakers. If one amp is 100 watts, you'll need 1,000 watts to ensure you gain volume. 1,000 watts will very likely distort and possibly damage/destroy your present loudspeakers.
3 decibels gained by doubling the wattage is about what you would notice if you increased the volume control on either receiver from, say, 63 to 65 on the readout. It's hardly noticeable.
That's the difference when you double the wattage.
It's a consistent difference no matter were you do the doubling. From 1 to 2 watts, 10 to 20 or 100 to 200 watts, you will only gain an additional 3 decibels of potential volume level whenever you double the available wattage as long as the quality of the amp remains the same.
For the most part, ignore wattage claims from any receiver. Shop for quality, not quantity.
The average 2 or 3 way loudspeakers are "active" devices. Unless your loudspeaker has only one single driver (speaker), the system must use a "crossover" which contains capacitors, resistors and inductors to "shape" the frequency response of the system.
The amplifier sees these collected electronic components as "the load".
If you want a fairly dry read, here's a bit on impedance and phase; http://www.stereophile.com/content/measuring-loudspeakers-part-one-page-4#zQ7CJF qsSVXmhMd8.97
What this boils down to is the average speaker is never a single "8 Ohm" load for the amp.
If all speakers were a single impedance load at all frequencies, amplifiers would be easy. They could be very simple and very good at minimal cost.
Unfortunately, companies such as B&W have produced systems which are not very amplifier friendly. They have excessive "capacitance" or "inductance" across their frequency range which will require higher amounts of "amperage" from the amplifier. For most AV receivers, this is where Amperage (and cost) come into play.
"Wattage" is a function of Voltage and Amperage together working into a "load". While it is somewhat simple to design an amplifier that tests well when run into a large load resistor on a test bench, only those single driver loudspeakers begin to approach such simplicity when it comes to the amplifier's capabilities.
For the most part, it's safe to say that most 8 Ohm loudspeakers will dip well below 8 Ohms. Most 4 Ohm speakers will dip beneath 4 Ohms. As the impedance drops, Amperage (or "current") must replace Voltage from the amp to maintain the same wattage output.
Due to the compromised design of most mass market AV receivers, this current delivery is a difficult task for the amplifier. If the amp cannot deliver and sustain high Amperage into the speaker load, the system will, first, overheat and, unless you reduce the volume levels immediately, it will eventually shut down trying to protect itself.
Buying a heavy duty power supply is the best bet against insufficient Amperage delivery.
Good power supplies cost money.
While it is true "class D" amplifiers do not require the same amount or type of power supply as a typical mass market AV receiver's "class A/B" amplifier, class D can still have trouble when the load impedance strays from a solid 8 Ohms. If you were to connect a class D amp to that single driver loudspeaker (or a very stable load multi-way system), the amp would perform well and can cost less than a "traditional" amplifier, even when used in an AV receiver.
Unfortunately, most class D amplifiers found in AV receivers are still not well suited to a loudspeaker such as the B&W's. Even more unfortunate is, most AV receivers do not perform to their best abilities when asked to drive the B&W's.
Of course, "best" is subjective and you may feel there is no problem as long as the receiver doesn't shut down. My opinion doesn't need to be your opinion.
I would not - and did not - suggest class D amplifiers simply because, as a group, they are still not well suited, IMO, to driving your B&W's.
I'll stand by my original advice; buy a "conventional" AV receiver. Don't bother with class D unless you have sufficient money to spend on very high quality systems.
In a conventional amp, the heaviest amp is most often the best choice for the B&W's. Avoid being drawn in by less than useful features and spend your money on a quality amplifier.
When comparing two AV receivers, if one has more features, the production cost for those features must have come from somewhere. In the mass market products of AV receivers, the most likely place for a manufacturer to take away cost is by building a lower quality amplifier.
Watts are cheap these days. You can buy 'professional' amps from Crown or Behringer for a couple Hundered $$. Even the kilowatt amp from Wyred-4-Sound is about 2.50$ per watt.
But, it is ALSO still true that if you simply LOVE 2 speakers, the one with the higher sensitivity will make better use of amp power. All Other things being equal. Even this 'rule' depends on the 'goodness' of load. High sensitivity speakers with problems in that regard are no better than speakers of lesser sensitivity which appear to be more 'resistive' to the partnering amp.
Since little REAL information is available and few besides Stereophile measure such stuff, you are sort of at the mercy of a GOOD sales guy and the minimal amounts of literature available from manufacturers. I would suggest that MOST speakers for HT use and marketed as such are 'easier' loads with the knowledge that MOST people will not have the robust amps necessary for some of the wackier stuff which has come down the pipe over the years.
Some lines, like Thiel and B&W can have a reputation for difficult load speakers. Maybe NOT the best partnering speaker for even a mid-line HT receiver. I saw the guts of a Thiel many years ago. The Crossover had about 30 parts on it including a half-dozen inductors. The board was about 10"x18". a MONSTER. I rather doubt that speaker was amp-friendly.
And than their are speakers like my Panels. Very Low sensitivity. But also a fairly benign load. Any reasonable amp will work. But in larger spaces or at the highest levels? You'll need a REAL rock crusher. I run 2x200 watts PER SPEAKER and that is OK.
Sorry for the late reply and thanks for the reactions! I couldn't respond in a timely manner because of Christmas ;)
I'll get a (normal) receiver with a high quality power supply for sufficient amperage. And since the amount of watts doesn't matter very much, I'll just get the most heavy receiver within my budget, from Marantz, Denon or Harman Kardon.
Keep in mind, since your speakers are not super easy to drive (though hardly the worst), the amp will be producing higher amperage/power than it would normally be asked to provide with a simpler speaker load.
Your speakers are, luckily, slightly higher in their stated "electrical sensitivity", which is helpful. Just as you only gain 3dB when you double power, you lower power requirements by having a speaker that is 3dB more sensitive to incoming wattage.
Therefore, with your 90dB rated B&W's, you can consider the amp to sound "twice as powerful" as the same wattage driving a more average 87dB (or lower) loudspeaker system. High power (as stated in wattage on paper) is not the most important spec with your speakers.
50-75 watts per channel should be more than sufficient unless you tend to listen at very high SPL's to extremely dynamic material. Explosions occurring in games and videos is very demanding on an amplifier. Still, given the sensitivity of your speakers, 75 watts really should be sufficient and even going to 150 watts won't gain you much extra room. Most amplifiers can actually produce power in excess of their RMS rating for brief bursts. In most cases, you can rely on this fact as long as the source material is not chock full of explosions and extended demands on the amp.
The less the amp has to work, the happier it will be in the long run. The harder the amp has to work, the more heat it will produce. Heat is bad for the life of the component - though somewhat unavoidable with amplifiers.
Make sure you place the receiver where it will have good ventilation. An open or top shelf is best. If the receiver must go inside a cabinet, it should have as much free air space surrounding it as you can possibly provide.
Do not place another component directly on top of the receiver or immediately to its sides. If you look through the top cover of the receiver, you might be able to see the finned heat sinks of the output transistors. If so, this is the area of the receiver which needs the most air circulation around it.
In the most extreme cases, small pancake fans can be placed above the receiver to draw air from beneath the unit, through and over its heat sinks. Drawing air through is far more efficient when it comes to cooling the amplifier than is blowing air on or across the amplifier.
If you are running a powered subwoofer, that relieves a good deal of the bass frequency's power requirement from the receiver. Bass is the most demanding frequency range when it comes to power requirements. Woofers in your speakers normally see as much as ten to twelve times as much power as will the tweeters.
Using the built in crossover you'll find in most AV receivers will roll those bass frequencies off beneath your set cut off point. The amp will not be asked to reproduce the deepest, most demanding frequencies. That also helps.
Again, that's a start where power reserves are considered. When power is conserved, heat is lessened.
I would though suggest you keep tabs on the heat being produced by the receiver during louder listening sessions. Ideally, you should be able to place your hand on top of the receiver above the power transformer and the amp will be running cool enough to leave your hand resting there for at least 30 seconds.
Ideals are not always in the design of a mass market AV receiver however. If you put your hand over the receiver's transformer and you can't touch the top cover for more than a few seconds, IMO, the amp is running too hot. That sort of heat will eventually destroy electronics.
Allowing the amp to get hot and stay hot means you are cutting down on its useful lifespan. Even if the amp doesn't go into self protect mode and shut down, you are damaging the components. It's then time to reassess your location of the receiver or add that pancake fan.
You haven't mentioned other speakers. The better AV receivers have power supplies which are separated and regulated individually. This has been a common problem with AV receiver specifications. They may state RMS power with only one channel operating. The true power available to the speakers drops considerably when other channels are being driven.
One more thing to look for - and which will normally be the case with the heavier receivers - is a stated wattage that says it will be produced with all channels driven simultaneously. You will be paying more for lower claimed wattage but this will probably be, in the long run, the better amplifier. When the manufacturer is willing to say more precisely what you are buying, they are also probably willing to build a better product.
Otherwise, most AV receiver specs are rather useless when it comes to deciding the quality of the component. THD is a negligible value when it comes to specs. Ignore it.
Most AV receivers are actually sold on the basis of the rear panel connectivity and the remote control. Select your best match by looking ahead to the components you need to connect now and in the near future. You don't need two or three ways to connect the same device so there's no need for all those connectors on an average consumer level AV receiver.
Buying the simplest component most often assures you will have the component with the best overall quality inside. Not always but often.
If you are familiar with the idea of selling the sizzle and not the steak, that's the AV receiver market in a few words. Most manufacturers are selling sizzle and buzzwords while leaving the actual quality of the steak behind. Don't get pulled in by window dressings.
HK is promoting a "green" technology in many of their products; http://www.automotive.harmankardon.com/en/innovations/greenedge.aspx
When you see an amplifier manufacturer state as high as 90% efficiency from their power supply, they're talking class D amplification. A typical class A/B amplifier will have a power supply more near to 50% efficiency (at best).
I like HK and I've sold and owned HK products since the '70's. I would, however, be hesitant to recommend HK "green" technology given your B&W speakers. You might contact HK if you're interested in their product and discuss the issue of your speakers and their amp.
Like LED lamps and hybrid cars, class D is the future. The future depends though on speakers that are far more amplifier friendly than the average B&W.
Good luck. Report back and ask any questions that might arise.
Just keep ANY new receiver as well cooled / Ventilated as you can manage. Definately NOT in an enclosed 'box' or with some OTHER bit of electronics Stacked on Top.