Those are fair enough reasons. Heck, you don't need a reason other than, 'cuz I want to!'. Again, just curious.
Going with the bookshelves also leaves you with a nice pair to do *something* with in the future if you ever upgrade, as opposed to a center that can really only ever be a center.
If you are using a second receiver to power the centers, you could buy a mono-signal splitter to wire between your pre-amp and the second receiver/amp. Split the center signal into two channels (L/R, perhaps) for the 'powering' amp. That would eliminate the problem of dipping the impedance too low with the parallel runs if you were going to try 6 or 4 ohm speakers. You could even adjust top-to-bottom balance by adjusting L/R balance.
I can say that I really like my VP150, and have nothing but positives to say about it.
Good luck!
