Denon has Audyssey, something others can't match.
Except that it's completely subjective whether Audyssey actually improves anything.
Personally....
I tasted Audyssey MultEQ when I owned an Onkyo 876. Completely unimpressed with the changes that it felt were necessary. Made the sound hollow and weak, and completely screwed up the 3-dimensionality of the M80's in stereo mode. Off, thank-you-very-much. Perhaps Denon does it better.
My old Pioneer has their {very} early MCACC system, and I've never been impressed with it either. I leave it off. When I recently owned a much-newer Elite SC-05, its new-and-improved MCACC did a fair job. But only just. The changes it made weren't as offensive as what Audyssey wanted to do, but I still didn't really think it improved the overall soundstage much. Just kinda made it sound, different. Turned that off too.
Perhaps I am just a Luddite when it comes to sound processing, but I've yet to hear any system that's better than one's ears, a little attention paid to speaker positioning, and a classic Radio Shack SPL meter. Yeah, get off my lawn, too.
So I guess my $.02 would be to buy an AVR that has the features and specs that look best to you overall, and not base the decision purely on Audyssey vs. MCACC vs. {whatever}. Personally, my next AVR is likely going to be a Denon, simply because I'm ready for a change away from Pioneer (had my 43TX for 7 years now, and was sort of mixed about the SC-05), and Denon AVR's seem to have an astoundingly happy group of followers, both here and in other forums. It just seems that I read of far fewer complaints of Denon gear than I do of any other manufacturer. They seem to build very robust and high quality AVR's that play well with other gear. Both in terms of 4-ohm M80's, and in connectivity to other equipment. Unlike Pioneer, where certain HDMI features only work if you have a Pio HDTV; which I think is BS.
I will say this though, at the risk of provoking the ire of the "amps don't matter club", I felt that the SC-05 did really make my Axioms sing. I can't prove that it had anything to do with the ICE amplification, but the sound coming from my Axioms was *damn* good. Extremely clean & clear dynamics, with amazing dimensionality, up to ear-splitting levels. Really, really, really good sound. Even on my M80's, which, with their 4-ohm impedance, aren't technically supported by Pio Elite AVR's. Had I kept the SC-05, I would have dumped my LPA-1, no questions asked.
Good luck! Fun times, buying a new AVR.
