You could go with 2 sets of BP2X's if you like the sound. If I was going 7.1, that's what I'd do.
Make sure you take pics of your completed setup so that I can be highly jealous.
Oh, and I'd personally still recommend a separate subwoofer to really add punch to your setup. Those 8" subs are definitely nice for filling in the low end, but I wouldn't use them as my only LFE source.
I'm sure BigDaddy would agree, since he's running supertowers and 4(!) subs.
