Hey chess;

Try and see if you can borrow a passive preamp. That will definitely show if the issue is with your Denon or the amp itself.
I have tried an Anthem MCA20. I know the Bryston 4B outperforms the Anthem. Brystons has a nice warm sound. It has no hum and it runs only warm after 6 hours of running hard. It has lots of headroom as all Bryston's are known for.
I got a passive pre I can possibly part with for a short period of time if you wanna try. Leave me a pm if your interested.

Saturn

http://www.quadloft.com/hometheater- new HT