As far as the center channel, one way to save money and have more ideal sound is to have a third M22 instead of a VP150. If you can fit it into your space, that's what I would do.

I've never heard the lower-end, non-DSP Axiom subs, but the general consensus seems to be that you can get more value with other brands. If a matching look is important to you, though, then that's a consideration.

That being said, I'm sure that system would sound great.