Is there a nice RNS-E FAQ or wiki somewhere?
 

Have VAG-COM, have about half a clue about retrofit and such.

Trying to understand what the possibilities are for the '07 A3 I'm about to buy.

RNS-E nav - seems pretty straightforward.

XM module - still do-able?

Bluetooth - just another add-on module?

Besides navplus.us, what other sites should I take a look at?

SD card reader - what all can this do? Is it on all RNS-E?

There used to be a (rubbish) page on Wikipedia, but thankfully...
 

Wikipedia deleted it.

Ask your questions on navplus.us and you'll get them all answered by guys who know.

XM/Sirius - yes.

Bluetooth - another module plus antenna and microphone.

SD cards - plays MP3 files and shows track names on the DIS. Works with SD cards only, not SDHC cards. Limited to 400 files.