I have a Kewood head unit that is SIrius capable connected to a SIR-KEN 1 tuner attachment. Does my subscription run with the head unit or the SIR-KEN tuner? I want to replace the head unit with another Kenwood head unit that is compatable with the SIR-KEN tuner, that is, use the same tuner. Do I have to have Sirius transfer my subsciption?