If you can fit 3 M80s and don’t mind the cost then do it. That’s what I have and can’t imagine going back to either the M22 or VP150 center and my room is only 13 x 21 x 8-11 (vaulted) with my seating about 10‘-11‘ from the center and mains. The M80s and M22s sound very similar IMO.
IMO a single M80 sounds much better than adjacent M22s. However, I only tried that on either side of a HDTV and not under my screen. It’s likely having adjacent M22 enters will sound good for movies creating a little more wall-of-sound effect however, for music it will spread out the center channel making vocalists and instruments sound wider thus likely messing up the front soundstage.
Like John suggested above you might want to try the M22s out in that room to get a feel for how they will sound especially the highs.
