tobz67,
I have actually never listened to the VP100, so I can't comment on a comparison with the VP-150, but I do own the VP-150, and it is an excellent center channel. Dialogue is crystal clear, and there is nice dispersion of sound.
Maybe others can provide more detail, but I think the easy answer is this--the VP-150 is a better speaker than the VP-100. Whereas you can't necessarily say that in regards to M3's vs. M22's, since they have different tonal characteristics that might appeal to different people differently, and one is not clearly better than the other, I think there is really no reason to go with the VP-100 if you can afford the VP-150.
