Satellite radio in car?

We just purchased a 2007 Dodge Caliber R/T, and it has basically every option. While reading through the owners manual, we learned that the lower models came with a radio that was XM or Sirius ready (can't remember which). For some reason, the upgraded system, with the 6 disc changer and better speakers isn't satellite radio ready. I would like to get satellite radio for my wife. Is there anyway to get it integrated into the vehicle better so I don't have to have one of the receivers mounted in the car?