[QUOTE=UCrewX5]To install Siruis in your 540 all you had to do was replace your radio module with one from a 2004 or newer.QUOTE]

That's what I get listening to the steeler. I used to have a '02 525 and wanted to do just that. They told me it was 'cost prohibitive' to change out the parts. I just didn't bother this time and went right to aftermarket. Not a factory look but doesn't look tooooo bad. It also gave me the opportunity to update the rest of the system in one shot - speakers, amp, sub, etc.