AJ, welcome. In general I'd suggest that using three identical vertical speakers across the front would give you the best sound. From what you describe, the placement of the center speaker is going to be a problem, but can you place the M22 on the floor directly below the screen and possibly tilted up a bit? All sorts of wall or ceiling mountings have been used(even hanging from the ceiling by chains)and possibly some may comment on that.

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Enjoy the music, not the equipment.