Yup you could either sell it and add the no xm issue to the description, or keep it for the faceplate bezel and buttons.

Alot of grand prix's dont have xm, also the 6 disc works in non monsoon grand prix's as well. The headunit will recognize the absence of the amp and change the settings accordingly.

Many used 6 disc radios have worn buttons really bad but with your mint faceplate you could rebuild it the right way by using your faceplate minus the display board on the new one you buy,haha