z4 Rear speakers quit

In my 2003 Z4 the rear speakers have quit working. It is a brand new DSP head unit and I am wondering if the AMP has gone bad. I checked all of the wiring and fuses. Can anyone tell me how to test if the amp has gone bad?

Thanks

are you sure it isn't just a connection not hooked up, since you did just replace the head unit??

I just pulled the dash out and rechecked that it was connected right. Unless there is some trick to it I don't thinkk that is the problem. On big plug contains all of the wires.

u can take a double a battery and hook up a wire to each end and touch the positive to the positive and negative to negative on the speaker and it should make a noise but disconect the speaker from the factory

Okay I have confirmed that the amp is bad. Does anyone know a good place to get it repaired? Or a good place to get a used one?

Thanks.