FWIW, I have a 400 sq ft family room with a 16 foot ceiling. I have the same setup as you, except I have a Denon 1802. Just speaking from the range on the volume dial of 18 to -60, when I have it in the -10 to -15 range, I can't hear myself think. Most people will say the M80s can play even louder. How much louder do you need?

I think you'll be happy with the M60s.

John