I am planning on buying a new 6.1 receiver, and buying Polks from Crutchfield. I will be buying Left and Right Rti38's and Surround Fxi30's. Now, I can either buy another pair of Rti38's, use one for the center and one for the center rear, or buy 1 Csi30 for center and forget the rear center. Which would be better? My room is small, so the rear center isn't a big deal.