I have the HK 630 (from onecall.com) and think it is a great unit and I also have the M80's. The only issue I have with the HK 630 is it tends to run a little hot. I don't know if that is because I'm running the M80's or not, but my guess would be yes.

I keep another external fan on it to keep it cool (check the link in my sig). I don't know if the Denon 3805 has better ventilation or not, nor do I know how hot it runs with the M80's. Maybe a 3805 owner with M80's can post a reply.

Shag