Welcome back to the forum!
The M80's are relatively easy to drive so the Pioneer should be Ok unless you are trying to achieve some very loud levels.
Does you avr have preouts? If so then simply adding an external amp is the cheapest option. I have been looking at used amps and there are many to choose from, so many I am undecided as to which to get. Emotiva and Outlaw Audio are 2 ID companies with good reviews, the latest XPA series from Emotiva seems to be playing nicely with the M80s now.
As far as a full M80 system, unless oyu have lots of room I would stay away from this idea. I have heard Mel's(onn) full M80 system and it does sound great but I think I prefer the QS8's for surround duty with movies. The M80 system excells at multichannel music though.
