Regarding the Denons running subs hotter. My Denon 3806 has an obscure, hard to find, sub setting that defaults to +10 and can go as high as +15. This is over and above what you set your sub up for in the general speaker setup section.

Somewhere you can read a post about my sub woofer gone wild until I discovered this setting.

With great power comes Awesome irresponsibility.