I have a 7.1 setup (four M3's, two QS8's, one VP150). I am redoing my room and I am debating changing my two M3's in front to two VP100's. The primary reason I am doing this is I run a front projector and it would be a very nice room layout to lay them all out in front below the screen. Anyone see why this may be a bad idea (I assume it would be better than just turning the M3's on their sides). Thanks!

You can find out by ordering the vp100's and comparing them to the sideways M3's. It may cost you the return shipping fee to get the answer. I'd bet the M3 on its side would sound as good as the vp100 and neither will have as good horizontal dispersion of the tweeter output
as the m3 upright, which will degrade the all important sound stage.

I hope you decide to do the test and post the results.

An interesting idea indeed.

Yeah, my major concern would be the relatively poor horisontal dispersion of the VP100's. Perhaps, triple VP150's would be very nice!