I've had two denons and have always though they rolled off the highs a bit.
I currently have an integra 7.4, its a few years old (and made by onkyo)
It is exelent in build Q and SQ, but one thing I noticed (as in most modern receivers)
it sounds better with all channels engaged, of course.
I am currently running B&W speakers on mine, they are notorious for their inefficiency,
but the Integra never wavers, even at high vollume levels.
And Onkyo also pays attention to the audiophile, with phono stages, pure stereo
mode which shuts off the sub and runs all sound through the fronts, and the ability to turn off the display, etc.
And dont worry about the heat, mine has an inch clearence and does get a little hot but I keep it on for hours and no problems yet, and its really refined too, but maybe thats just what you get for the "high line" integra" version