Update:
I've done further testing with the C40 and B-15's. But I won't bore you with the details because I just got the PSB C60 center. So without further ado...
This is a large centre. Compared to the VP150 it is 1/2" narrower in width, 1" taller and 3" deeper - if you don't count the curved front speaker panel and grill, then 12" deep! It's dual bass ported with a single 1" tweeter and 2 x 6-1/2" drivers. This proved to be a much better match to my bookshelf's 7-1/4" than the C40's 5-1/2" drivers.
I put on several Dvds that I've been testing with and the sound displayed a noticeable improvement. This blends as near perfect with my speakers as I could hope! Like the C40, the highs are still crisper than my speakers but less so with the C60. Blending of the mid/bottom end was beautiful. The front sound field seemed to envelope my display. Dialog and effects were very clear and clean! No occasional boxiness or compression compared to the C40 and particularly my old center. When played really loud, louder than I would ever listen, dialog started to sound a little artificial. A little tweaking proved to be all that was needed. The center's dynamics easily matched my speakers and perhaps a little better! I'll have to get my work's SPL meter for a proper setup. I'm not through testing but so far this center seems a winner!
I realize I'll have to upgrade my fronts and surrounds but one step at a time! I'm still hooked on adding the QS8's. The demo at jakewash's proved their worth! My only concern are it's 5-1/2" drivers. If, like the C40 issue, I experience a more pronounced mid-high to high this might prove distracting. Again tweaking might help to correct but...I wish Axiom made a larger version.
Perhaps if I can convince the wife, towers might be a possibility!? I could easily pick up PSB towers but some Axiom M60's or even 80's would make a very nice addition! I know the inherent problems in mating different speakers but if properly matched, like the center, it is possible!
