I had an Elite VSX-59 a few years ago. What a beast!
In all reality, it tough to hear a real noticable difference in receivers in about the same price range and "category". By that I mean consumer level vs. boutique brands like Arcam, NAD, Rotel, etc. which I really don't have much experience with.
I have owned 20-25 different receivers over the last few years (I think I have 4 on hand right now?). To me, the biggest difference between them is how easy they are to setup and live with. I'm a tweaker so H/K is out. No manual adjustments to the EZSet EQ.
Those with Audyssey and Yamaha are O.K. with at least some manual EQ setting. But Pioneer wins with 6 MCACC presets and a ton of audio adjustments.
As for a "clean" sound, the one that pop's into my mind first is also Pioneer. They've never been called a "musical" receiver (whatever that means) but I've always thought they were crystal clear, especially those that are Air Studio certified. But again, if someone came along and said I was nuts for thinking I could hear a difference I wouldn't/couldn't argue with them. But look for a good SC-05/07/25. The SC-27 and newer are tough to find in good shape for $500. I'm using an Elite VSX-23 in my family room and see no reason to replace it.
Onkyo/Integra were the price/feature leaders but their hdmi boards have a high failure rate. Denons of that era were a nightmare for me to setup and operate so I've never really considered them for long term use. Yamaha is the one consumer level brand that I haven't owned yet but I rarely hear a bad thing about them.
One old-timer that I'd like to mention is the Adcom GFR750HD (the HD added hdmi video up-conversion). It only has two hdmi inputs but they worked very well (un-like teh H/K 745 I had) and that 145 wpc amp and the other high quality audio circuitry made for an excellent sounding receiver. But it was a little more difficult to live with simply because it was their first (and only?) attemp at HDMI and the remote was somewhat old-school.But the core audio performance rivalled, and maybe surpassed, the best that H/K has ever offered. Which was quite a lot with the 7200/67300/745 and 7550HD. They pop up every once in a while, usually for well over $500 but +/- $400 is more like their true value. I think I should have kept mine. An Adcom 750HD and OPPO BR player would be a tough pair to beat in SQ.
If you stretch the budget to $600 then look for a Pioneer 1124. It has the Sabre ESS DAC's in it. Should sound wonderfull if it's anywhere near the OPPO 83se/95/105.
If you can do with hdmi then an H/K 7200 and Oppo 83se might just be the best sounding electronics I've had so far.
"Everyday room": Panasonic 58" Plasma, Dish HD DVR, Pioneer Elite vsx-23, BDP-23 BR, dv58avi universal dvd player, Paradigm Studio 20 V1, CC-450, Dayton HSU-10 subwoofer.
"Movie/Music room": Toshiba 65" DLP, Dish HD receiver, Marantz 7005, CC-4003, BD-7006, Polk LSI25's-LSi7's-LSiC, 2 original Dayton 10" "Mighty-Mites" subwoofers. (subject to change without notice).
Also have MB Quart Vera VS05 +.....too much to list. Help me.