If at all possible, mount the bookshelf M22's on the wall for best on the wall sound, I would mount a painted board to the wall, then mount the M22 to the board. I'm using two 1/2 inch boards glued together so I've got plenty of thickness for the screws. These can go good with a VP150 center, on wall. 2nd choice would be in/on wall M22's, and lastly the on-wall M22's.
I'm in the process of mounting bookshelf M22's above and below my TV, but got lazy and haven't progressed in a while. I really need to get this done. But, seems when it comes to getting things done, it's cleaning the house or yard work instead. Mama Mia!
