Bipole dipole questions

[navyman]

I am in the process of upgrading my home theater. I purchased an Onkyo 606 a few weeks ago and just took the plunge and bought polk monitor 70's for my fronts . My next purchase is either going to be a decent center channel speaker or some new sorrounds. The Onkyo is capable of 7.1 but I think i am going to bi-amp the fronts to maximize their preformance and just use the Onkyo as a 5.1 system. Plus it will result in less wires that I need to route through my apartment.
I am upgrading from an onkyo htib. It was a stupid idea to buy a htib and I probably won't be able to salvage any of the speakers that came with it. Now for my center speaker I have been looking at some of the polk line and they suggest the cs-2. I was wondering if there are beter alternatives and if spending 400 dollars for a center speaker would match up with the 70's.
My main question however is in regards to the surrounds. The whole bipole dipole thing has really caught my attention but I am not sure if my setup could take full advantage of this feature. I was looking at the polk fx4's and they are beautiful speakers. If anyone can give me any suggestions I would greatly appreciate it.