All three Denon's I've owned have driven the M80's with no problem, the 3808 would have no problems at all with 4 ohms. I would guess the Pioneer should be able to drive the 80's also, but If I had to choose between the two I would go with the Denon.
Depending on your budget the EP400, 500 or SVS are all great subs, HSU has some good offerings also.

A computer once beat me at chess, but it was no match for me at kick boxing.