I wouldn't be surprised that it sounds like bad mp3 compression, because, in a sense, it kind of is. Sirius' content streams at 128kbps; for most people, it doesn't sound that bad, to others it does - to each his own. But if it sounds as bad as you make it out to be, then I would have the dealer check it out, maybe there's bad wiring in the antenna or between the connection from the antenna to the head unit. If you encode the songs on your iPod at 128, and Sirius sounds significantly different compared to your iPod, I'd get that checked out.