[TeddyBGame]

From what I understand, the OEM XM/Sirius tuner uses the CAN bus to change channels etc. It also uses audio inputs from the CD changer harness/connector area.

See link to Lee's OEM Sat upgrade on his 2001 A6...there is a pdf doc to access:
http://forums.audiworld.com/a6/msgs/496938.phtml

I would be surprised if the part# for these OEM XM/Sirius receivers are for different hardware. If they are...it probably has to do with the fact that an B6/B7 A4/S4 and a C5 A6/S6/RS6/allroad require a slightly different mounting point etc in the trunk. Similar to the various audi part# for the TMC/CAN gateway for the CD-based Nav.

Just a theory.

Good luck!

 

[TeddyBGame]

again..thinking out loud:

It's possible that the RNS-E (R = US version) is only capable of supporting either the OEM CD changer...or the OEM XM/Sirius module....but not both.

However, the C6 A6 (2005+) can support a glovebox CD changer and the OEM XM/Sirius. And thats a similar MMI setup...but based on the MOST network.

Not sure.

-ted