I had M22s and a sub in a room pretty much the same size and not once did I even wish I had gotten the M60s. While not huge, the M60s are big and unless you stick them right up against the walls or in the corners -- which is highly inadvisable -- they'll take a bite out of your floorspace.

In that size room, M22s + sub will be much mmore versatile, though you will need stands or some other surface to place them on.