Yamaha produced a very decent line when they first entered the US market. Eventually, Yamaha began to produce gear that was mid-market and mid-fi. In essence, they became more "Japanese".
They were always very capable of building a good (but not great) sounding amplifier. But, more often than not, they had enough bells and whistles added to their gear that the sound got a bit lost in the translation.
Rotel is also a "Japanese" company. There's no way to tell you how the two components compare when I have no reference for how you feel the Rotel performs.
Either amplifier would be placed in a system and the system's overall personality is what's more important than the individual component itself.
I don't have much experience with amps, this is my second amp, the first is Rotel. The speakers are Dali Concept 2. I'm not sure about specifications, for Yamaha I can see it only on the web page and it says 2x 60W an 8 Ohm nach DIN, in the Rotel manual it's 50W DIN Output 4 ohms and rated power 30W into 8 ohms. Can interpretate this specifications as they are approximately of the same power? It's tricky to compare amps because I must switch speaker cables constantly but to me it seems that Yamaha could be a better match for Dali speakers as it has more bass than Rotel and that's what this speakers need. Rotel's bass is tinier than Yamaha's and maybe more "punchy". The mids on Rotel sound harsher so the vocals and acoustic instruments sound more pleasing on Yamaha and it seems that Rotel has clearer treble, Yamaha can sound muddy but it has an equalizer which works well for bass but less for treble, that's my impression. Buzzing sounds of acoustic guitar often sound strident on Rotel. Yamaha sounds "bigger", with more space, and maybe less definition which kind of works for me because my room is small and not very acoustic. I don't have other speakers to test the amps so this is for Dali speakers. I bought both amplifiers used, but Yamaha for much less money (about 30$) so I wonder how it could be that this Yamaha sounds more satisfying in many aspects or it's just a better fit and that's all? What used bookshelf speakers in this price range (about 100$) would than be better fit with Rotel amp? Some that could deliver a little bit more bass and have mellower mids and highs perhaps? I know it's all a matter of experimenting but I need some reference points. Or I could just sell Rotel and buy some other amp for the other system...
Now after some comparing, I find Rotel has better sound than Yamaha, it's less "washed out" but it lack bass and lower mids on this speakers which Yamaha delivered so it seems that it would be interesting to buy some other amp, I can get Yamaha A-550 or R-3, Technics SU-700 or SU-VZ220 used here, maybe some budget NAD would fit? I'm not able to spend much money. It's also possible the other way around, to change the speakers but not bigger than Concept 2 because there is not enough room for bigger speakers. I'm not going to hurry with this anyway...
Have you done a proper speaker set up? Do you have the speakers mounted on good stands?
http://www.tnt-audio.com/casse/waspe.html
Set up is most often the most frequently lost step in consumer audio. Have good stands and set the speakers up to provide the best performance possible in your room. That eliminates the speaker position as the influential aspect of which amp to buy.
After some more listening and comparing, the conclusions are more or less the same. Yamaha gives nicer bass, more pleasing to listen to, no matter what volume or eq setting, it's just sits better in the mix immidiately, and the vocals sound better, but the whole sound appears as if it's compressed a little or further from the listener. Rotel is more deailed, reveals more subtle qualities in the sound of instruments which is inviting, but the sound as a whole is disbalanced with this speakers in this room. There is no room for experimenting with speaker position because the room is small (15 m2), the speakers are on the wall stands (which are not bad), I applied basic rules for distance between them and from the listener, tried many positions (closer to the wall, further, etc.), there are just few possible positions, and there is no space for floor stands to try that. My conclusion is that this Yamaha is not a perfect choice but it helped me realise that I could get a better sound if I change the amp and also I will try Rotel with some other speakers when I have an opportunity. Thank you for your help.
You are building an "audio system" or, more accurately, a "music reproduction system". Each piece of the system is as dependent upon the others as is, say, aperture, shutter speed and ISO (sensitivity to light) to the Exposure Triangle of photography.
Using the exposure triangle as an example, if you alter the aperture of the lens, you must then change at least one of the other two legs to achieve an equivalent exposure. Or, you can alter one leg and split the difference in your adjustments between the other two legs. However, to achieve the desired results - a perfect exposure value - you must give equal sway to each of the three values as they operate in a conjoined system predicted by the rules of physics.
Audio is no different. Both audio and photography rely on principles of physics for their best results. If you do not comprehend the physics behind either, you will struggle to be successful with either.
You cannot take one value, say, your loudspeakers, and place that component value in a position which strongly disfavors the best performance and then expect to make up for that difference by playing with your amplifier. If you have purchased a speaker system which was designed for stand placement, then you will achieve your best results with the loudspeaker placed on a stand.
"Standmount" speakers have become the norm for the last few decades as they have replaced "bookshelf" speakers of old. Standmounts recognize the inevitable fact the speakers generate pressure waves into a resonant chamber, which is your room.
The position of your speaker system relative to that resonant chamber - and to your ears - is going to strongly affect the perceived sound at your listening position due to the reflective and the resonant characteristics of your room.
Once you say "this" is where the speaker systems must reside, you have thrown away 90% of the performance of the speaker system. In other words, you paid 100% of the price for the speakers but you've decided to discard 90% of their designed in performance.
Once you've discarded that amount of performance from one leg of your system, you cannot equally compensate for the deficiencies by playing around at swapping amplifiers.
It's the equivalent to a photographer trying to take a photo in a very dark location but insisting on an ISO value (a sensitivity to light value) of no more than 100 or as low a value as possible. Proper exposure is virtually impossible under those conditions and the changes in aperture and shutter speed which would be required to compensate even slightly would introduce other problems into the final product. That logic makes both photography and audio a function of the "systems approach" to thinking.
Ideally, you set up a system, discussing either in the purchasing of well matched components or in the set up of those components, in a logical, almost scientific, manner. If this value is altered, then the other values of the equation will suffer.
Begin making changes willy nilly and without a plan or a proper set up and you are simply asking for unpredictable and unsatisfactory results with each subsequent change you attempt.
That is simply saying, yes, you can change the amp, you can change the source, you can change this and that but the problem - the BOTTLENECK - remains the speaker position. Or, you could say, the loudspeaker system which is poorly suited for the position you have forced it into.
You purchased a standmount speaker system. Either you must work with a standmount system, or you should alter the speakers to reflect the position they must occupy. Until you match those two requirements, there will always be substandard results.
Putting it in more classic terms ...
Until you address the BOTTLENECKS in your system, you will always have the same results which are most strongly influenced by that BOTTLENECK.
Nothing you do can be better than the effect of the BOTTLENECK as it influences your entire system sound.
Those are simply the facts of how you build a decent sound system if high quality music reproduction is your goal. I'd suggest you forget the buzzwords of audio and concentrate on the purpose of a music reproduction system and the physics which predict the results.