Hi Danno,
How big is your room (length,width, height) and do you like to listen at insanely loud levels, like a few people I know?
If so, then definitely consider using a separate power amp for the M80s, with a rating of 150 to 300 watts per channel into 4 ohms. You can use the AV receiver for all the other channels.
Beware of Onkyo and some other manufacturers' claims as to being "4-ohm capable". If it's based on a bogus "dynamic power into 4 ohms" rating, that means it may drive a 4-ohm load for a fraction of a second, then overheat and shut down.
If deafening playback isn't a requirement, then at Axiom we know from customer experience (as well as having a number of different brands of AV units in our listening rooms) that any Denon or H/K AV receiver , even their entry-level models, will drive the 4-ohm M80s with no problems. So will AV receivers from Sherwood Newcastle and NAD. The Pioneer 1015 with MOSFET output devices will drive the M80s just fine. The aforementioned are the only brands I unhesitatingly recommend if you are getting M80s.
