Which speakers are best for surround sound on a 5.1 Ch setup? I am going to use the surround for watching movies from DVD only. A bi-directional surrounds like the (Polk FXi3) or a front-firing like the (Polk R50). Currently I own: Center: Polk CSi3 L/R: Polk RTi10 I am using a old Yamaha receiver and I am planning on replacing it with something more powerful.