Denon is worth looking at also, but the Onkyo isnt bad, even w/the weaker power supply like Berny stated. I think the pioneer elites are way overpriced, and would stick to HK, Denon, or the Onkyo. JMO
Onkyo power supplies are simply terrible. Sound and Vision magazine two years ago tested the top of th eline Onkyo 901 (I think that was the number) rated at 125 wpc. Well, when you connected five speakers, the power output clipped at 58 wpc. Tested seven speakers (a 7.1 setup) and the power dropped to below 54 wpc. This is because Onkyo uses weak power supplies and only rates their receivers driving only two channels at a time. The resulting sound can often sound strained and weak.
Of the units you listed, only the harman/kardon and the Pioneer Elite will produce their rated power. Both are very good units.
I've never liked the Yamaha/Denon Klipsch pairing, I think that it is too harsh. But that is judging from my ears, you should hear it for yourself. I prefer the Pioneer/Klipsch combination.
Klipsch speakers settles it in my mind. Klipsch are very forward, somewhat bright sounding speakers. Mating them to a Yamaha, which is amongst the brightest sounding receivers out there, will make the system sound pretty edgy (not in a good way). Either the h/k or the Pioneer Elite, both of whom have a much more reserved, laid back sound, will be a much better match for the Klipsch speakers. The end result (which is what counts) will be a very nice balanced sounding system that will sound the most realistic. Strongly recommend you actually listen to these receivers with Klipsch speakers before you buy.