try a DVD. The radio is 2 channel stereo. I guess you could apply a DSP to it to make it play in your surround speakers, but it isn't going to play in your sub because there isn't really any low frequency sound in FM radio.
A DVD will have a 5.1 channel soundtrack. The "5" stands for your 5 speakers (Left, Right, Center, Surround Left, Surround Right) and the ".1" stands for the Low Frequency Effects (LFE), which your subwoofer will play.
Your subwoofer can also play sound from the main speakers depending on how you set things up. But start with getting everything hooked up correctly and working.
