OK another question re this SAME issue. I have the Sirrus Xm app but my husband still wants to be able to pick up radio from Sat. There us already a sirrus antenna on our car but we put in a better radio. Do we just go buy another xm portable radio and have it work through the new radio we installed? Will it just hook to existing antenna? Do we need simply need an ADAPTER along with the new portable radio we are planning to get?