I run a Rotel RB 1080 for my M80s that I am very pleased with *but* if I was going to limit my budget to $700 or less a pair of these
Outlaw 2200 Monoblocks would probably find their way into my home. 200 watts at 8 ohms and for your 4 ohm M80s ... 300 watts per channel for $325 per amp. Not bad!
I'm looking at running a pair of center channels and am thinking about a 2200 to run one of 'em.