I don't know the details of the base radio, but if you can add a Sirius module to it, then you can work with the mod that kmoney made up. Of course that means you'd have to buy the Sirius mod, the parts from Radio Shack and build it up. I still haven't 'cause I don't have the know-how. Maybe kmoney could hook you up.
This is his solution:
Tech: AUX Input/iPod in Factory Radio
Hope this helps