It sounds like you were thinking of running a "fake" 9.1 setup, with a standard 7.1 setup but A+B speakers duplicating the front signals and the "B" speakers positioned up higher as pseudo "height" channels. Is that correct?
If so, it's a bad idea. Duplicating the front L/R channels through four speakers, two of which are positioned up high, will screw up the imaging of the front soundstage. I would rather have a proper 7.1 with two tall, high-quality tower speakers up front, that would give better sound quality than "faking" the height channels and probably cost less as well (not to mention easier to set up!).
Currently the first wave of "9.1" channels are appearing on the market, but they will be very expensive. The Denon AVR 4810CI is the first such unit, and Onkyo is coming out with a couple of 9.1 models as well.
I would strongly suggest you drop the idea of "fake" height channels and just run a 7.1 setup, whether that's 5.1+height or standard 7.1.