1) The "textbook" placement of stereospeaker is to make an equilateral triangle with the two speakers and the primary listening position. I would predict that your "alternative" location will work better for stereo imaging.
2) JohnK here is a proponent for a "vertical" center speaker, and I concur with the theory behind, e.g., a better horizontal dispersion. The M22 might be even better as a center channel if you can place it appropriately.
However, the M2 (M22) will NOT sound good when placed very close to the front wall. If you have to place the center channel like that, I would definitely go with the VP150. And even the sealed VP150 (or any other speaker) will sound better when placed away from the front wall.
