Your correct. A GM headunit won't recognize an auxiallary RCA signal (such as an empeg). The aux. euip. usually a cd-changer has to be able to communicate with the headunit to tell it to allow aux. play. There are aftermarket adaptors sold that will do this. They are described in the FAQs, but they will only work if you ALSO add a cd-changer. With help from people on this board I've been trying to figure out how the headunit talks to other components of the car but as far as your needs ....don't hold your breath, I'm finding out it's not trivial.