No question the 635...
A couple years ago, I "upgraded" an Onkyo 797 to the HTR-5790 due to the benefits of component video upconversion (especially with a ceiling mounted projector); however the Yamaha's sound was a step down IMO. It sounded brighter through my Polk RTi's, and often gave me a headache during a long, loud movie.
One day I found myself in Circuit City, A/B'ing all their receivers. As a strict bang-for-the-buck enthusiast, I never thought much of H/K (especially with their misleading "instantaneous amp" hype); however I found the 635 simply blew away every other receiver in the place, including their flagship Onkyo.
I'm not going to kid you that I could hear the difference between a gunshot from one receiver to another, but what the H/K has is "staying power". The scene that sold me on H/K was the bank robbery scene in Spiderman 2, where Dr. Octopus is throwing bag after bag of gold coins at a dodging Spiderman. I noticed that the sounds of individual crashing coins lasted longer on the H/K. In other words, on an Onkyo, Pioneer, and Sony each bag went "crashhhhhh" and often with an abrupt finish; whereas with the H/K, the bags all went "Crashhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh..."
I don't recall reading "instantaneous current" in my old Physics 3 book, but I noticed two distinct differences with H/K versus all other mass market receivers: weight and power consumption. The 635's 1000W rated power consumption rivals many power amp separates. Meanwhile the Yamaha's power consumption is a paltry 500 watts. (Note a Sony 998 is just 310W, while the mighty Denon 5805 is a circuit breaker busting 1430W!) If you live in America, your house runs off approx. 110V; divide that into the Watts, and you get the true amperage capability of each receiver's power supply. The featherweight Sony can put out 2.8 amps; the yamaha 4.5; while the 635 puts out a very respectable 9.1 amps. Not coincidentally, the weights of each model increases along with added power capability.
Well the real proof is in your ears, and I can tell you the H/K finally has my Polks signing like never before. Sure I could always fill my room with loud noise, but now the sound just gets loud, not noisy and never grating on the ears. And let me tell you those 75 watts easily fills my home theater with more decibels than OSHA would allow. DO NOT let the 75 watts vs. "110 watts" scare you for a moment (like it did me at first.) Just like a Porsche, a Kia Sedona can also go 0-60 in 4 seconds...so long as it is going down a ski slope with a 50mph tailwind. Yet that is about how accurately most receiver mfgs rate their amp sections.
Until someone smarter tells me different, power consumption is how I will base any future receiver or amp purchases, and with a big nod to H/K. Good luck!
