Well that depends on what B&W's he likes. I've heard their 600 series speakers and hated them. Their new 700 series sound great. (to my ears)
Go to your local dealer and listen to the new B&W 703 towers. That's pretty much the M33, M60, and M80 sound. Or better yet, as BigWill says, see if there's a local Axiom owner near you that will open up his house for a demo for you.
It sure seems as though your room is big enough to handle the M80's, but it's also not too big for the M60's. I don't know how loud BigWill is cranking his M60's but I've never had them so loud they started to strain. (And I've played them pretty darn loud!)
If you want a great two channel amp to add to your Pioneer to power the mains (whether it be the M60's or M80's) I recommend the
Rotel RB-1080, or the
Odyssey Stratos. Both are "giant killers", much like Axiom speakers are.
