I just bought an Onkyo 606, M22's, vp100, QS8's, ep350, and Panasonic 50PX80. I don't have any complaints at all, but also didn't have anything previously to compare the setup to.
Let me think about the Onkyo.. Maybe the best compliment is that I don't pay much attention to it.. I listen to the speakers, and watch the plasma, and the receiver just does it's job.
Feature wise I'm very happy. It has more options than I know what to do with, and has handled everything I've asked it to.
Power wise, I've had 1 DVD so far where I turned it up to max volume (original Matrix, seems to have only 2/3's the volume of any other DVD I've tried). Other DVD's I can get to about 65-70 (max of 80).. I don't have an SPL but at this level conversation with someone standing next to you is difficult, but not impossible. This is loud enough for me. My daughters (early teens) start to complain it's too loud much over 60.
CD's I turn it down a bit more.. most of them seem about 10-15% louder than the average DVD at the same volume. I haven't tried hitting 70 with a CD.. 60 seems just as loud.
Maybe one issue I saw, and have seen mentioned on the AVS forums as well is 480i sources. I saw a definite increase in picture quality after switch to component cables and 480p output on my dvd from 480i. I don't have the receiver doing any upscaling, just switching input source to the HDMI out to my TV. I have yet to have time to investigate the quality of the upscaler on the receiver (I sort of figure the brand new Panasonic should be just as good or better than the Onkyo 606.)
All in all I'm very happy with it. I had been looking at the 505, and comparable receivers, but went with the 606 mostly for the additional inputs, and Audio formats, but I'm really glad I did. My impression is I wouldn't be getting everything my speakers had to offer if I had any less powerful receiver. I think for some people the 606 would be a tad underpowered for anything more than M2/M3's.. especially in 5.1.
I wouldn't suggest going with anything less then the 606.. and if you like watch movies or listen to 5.1 music very loud, then maybe I'd suggest moving up a couple notches as well.. for my purposes the 606 does everything I want, and still has 5-10% left to give.
Gene
P.S. My basement room is ~14 by 15' with stairs up on one side, and 7' ceiling (open floor joist).
