I'm slowly building up my home theater setup. I got an TX-XR575 receiver and for now decided to go with cheapest speakers: X-540. Got front/center/back speakers wired so that the receiver drives them directly. The sub is a different matter. I can't figure out how to wire it. The receiver has a powered sub RCA output, I can also see a 3.5mm (stereo?) connector on the sub, but when I connect the two, no sound's coming out (I do have sub enabled on the receiver). The sub seems to work when I feed it through the front input. I'm starting to think that I cannot drive the sub on its own, without other channels. Any thoughts?