Was wondering if anyone could shed some light on placement of the 2 surround back speakers. I have a Denon 5803, and am using (2) Polk f/x 1000 bi-pole/di-pole. Need to know distance to space speakers apart. Room is 16' X 21' and will be used mainly for movies. Building walls right now and wanted to put in extra studs at the right spots. Did a search but did'nt find much, and the Denon manual is not much help. Thanks for any help. Paul.