Hi kcarlile,
Class A/B analog solid-state amplifiers are about 50% to 60% efficient, so yes, they do waste lots of power, but at least we can console ourselves that we're not using vacuum tubes! You can warm up dinner on top of most tube amplifiers; in fact, tubes don't even work until the heater element inside heats up (that's what gives off the orange glow so beloved of tubo-philes) and stabilizes so that the electrons will flow.
Anyway, digital amplifiers like the Axiom A1400, which I have, run tepid or warm, but never really hot (like those old H/Ks, which I also have!), because as their output increases, they become more efficient (at near full output, the A1400 reaches about 95% efficiency).
The ICE digital amplifiers developed and licensed by Bang & Olefson (Pioneer uses them in some of their receivers) also do not run hot. Panasonic has made some really cheapo digital AV receivers which should run cooler than analog, but I've never had experience with them.
The real problem is sticking seven amplifiers plus all the preamp circuitry inside of one chassis. In the stereo days, you just had two amplifiers to worry about, and reasonable heat-sinking would keep them from running hot. But now, unless you put either a cycling or constant-running cooling fan into a 7-channel class A/B AV receiver, it's going to cook!
Regards,
Alan
