I'm not much help, but I wanted to BUMP this for you Worf. Sometimes new threads get lost without members noticing them.
I can tell you that in general, it's not a good idea to place a vertical speaker in the horizontal position. Also, in general, it's thought by many here that the M3s have a slightly different sound than the M60s, so you
might be better off narrowing it down to the M22s vertically or the VP150s mounted horizontally.
Like I said... I'm not much help, but
BUMP! 
Welcome to the forums!
