I have an 05 A8L W12. I have XM but want to switch. I called the dealer and wanted to know what I could just buy the Sirius "brain" for and they quoted me $559.56. This seems way high compared to the $330-350 I've seen people paying on forums. Is this way to much???

 

I'm sure someone else has done this. I just want to know if this is way to expensive.