I just installed a home theater for a friend and am having some issues. It's a Polk Tsx series, SVS sub and Yamaha Aventage 810. For some reason I cannot get the sub to work, but I hooked up a Denon receiver i'd put in his living room and it worked fine, and would also work if I used the preout for the front speaker from the Yamaha. I'm assuming it has a bad subwoofer pre out? Is that possible or has anyone heard of that before? It has dual sub pre outs and I can't get either one to work. The only thing i'm worried about is he ordered it from accessories4less and it was a refurb, i'm wondering if that was why. Any input is appreciated, thanks!