Eric, I agree with the other replies which indicated that a horizontal M22 isn't the best idea. If you absolutely have to use that space in the entertainment center, M2s properly positioned vertically would fit(and incidentally, as I've often commented before, a third vertical M2 would make a fine matching center speaker).

The article Peter linked was interesting. In reviewing Energy Veritas speakers Tom Norton made some comments on horizontal MTMs beginning on the bottom of page 2. of the review. The comments and measurements page illustrate the problem with the horizontal orientation. Note the suggestions that if the center could have been turned vertically the off-axis response would have been smoother and that the smaller 2.2 vertical would be a better center.

Thanks all for the replies. I have considered the M2s but really wanted something a little more substantial. (they might be the only way) Unfortunately, inside the cabinet is my only option. I have emailed the company about using 2 VP100s and a center VP 150 so I'm interested to hear their response.

The problem is that the VP100s would have the same problem as a pair of M22s, as I read it. (well, they might be a little better...)

would the L/R VP150s be mounted vertically?

No; there's no point in that. Might as well get M22s if you're doing that. I was just saying because of the better dispersion of the VP150s, they might work as LR horizontal speakers.

In the right situation, .e.g. restricted shelf space, that might be a great solution.

Anyone with 3 VP150s want to try it? :-D

Company reps said they wouldnt advise it. My only other option is the M2s. I'm a little concerned they might be too "whimpy" for my room. Ugh! What to do.

Try one of the three choices, and send it back if you don't like it! That's what the 30 days is for...