So the consensus is, for volume levels below "risk of long term hearing loss" I won't hear a difference between what the Denon can pump out and what the Denon+Amp can pump out to the M80's and I'll have plenty of extra room.

For example, I read a review for the DVD-A disk of the 1812 Overture. It warned of speakers not being able to handle the sudden volume change that accompanies the cannon fire. If I pair the M80's with a Denon 33xx/43xx receiver I won't have to worry about things like that correct?

M22's x 3, QS8's x 4
SVS PC12-Plus, Denon 3311ci
Ear-to-ear grin? Priceless!