I can tell you I have the m60's in a 8,000 cu ft room and they are plenty fine with my Denon 2805. Now if your into turning it up so loud that the neighbors hear it at insane levels, you might want the 80's.

M80s VP180 4xM22ow 4xM3ic EP600 2xEP350
AnthemAVM60 Outlaw7700 EmoA500 Epson5040UB FluanceRT85