I am hearing the buzz about the built in subs with the 533 PT's, but don't feel I am getting the most out of them. I have a RXV 1500, and have changed the front speakers to large, and the sub to none. Is there another step I am missing? Are the L/R speaker cables the only connectors that need to be used? Or am I expecting too much from the built-ins? I am almost positive they (the subs) are not working at all. Is there another setting that should be changed?