It is my honest belief that the M80's will be a bit too much for that room size. I have M80's in a 22 by 12, and I find that to get them to sound their best, I have to play them quite loud, too loud for the room size, and I have to be very far back from them.

My guess is that M60's would suit you much better.

Also to note: M60's are easier to drive than M80's due to 8 Znom as opposed to 4 Znom of M80's.