The M80s are only a couple inches deeper and taller than the M60's, if you have room for the 60, I would bet the 80s would fit just as easily.

Going with the M80 in any size room you still have the benefit of the better low end and detail they offer, IMO.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70