j_garcia said:
I'd opt for the 4306 or 3806 with an external amp for at least 2 channels.
This here is good advice. I have a 3806. My mains are each 4.2ohms, center channel 4ohms, two surrounds each 5ohms (DefTech BP2000 mains, CLR 3000 center, BPVX surrounds). I've ended up adding an external power amp to drive my center channel alone and I'm having an old classic 2 channel power amp of mine rebuilt now to put in to power my mains. The system sounded good before when it was just the 3806 alone, but when I pushed the system to 'loud' levels, not blowing out the windows like you said, just like turning it up sometimes to hear throughout the house, things sounded harsh and the protection circuit actually kicked in a couple times at peaks.
As far as the amp difference between the Denon 4306 and 3806, there's not enough of one to justify the price increase for the 4306 if the bigger amp is all you're looking for. Probably the same power supply just rigged a slight bit different to get a tad more juice out of it. If the 3806 has all the features you want, buy it and like J_Garcia above suggested, get a decent external power amp (not the cheap Behringer that keeps popping up in posts) to power your mains. That should take enough strain off the 3806 to give you what you want. My center channel being handled by an external amp (Parasound amp) made some difference by itself. Doing the mains that way should definately help.
Hold off on getting a fan, just see how the setup performs once you get it and see how hot it gets. I may add a fan to my big external amp, but I'm going to wait to see how the temp levels are with just the heat sinks, I don't want added noise in the room from a fan if it's not absolutely needed, and I don't turn the volume up LOUD very often.