I have rented the A6 twice at MSP on PC upgrades (although it has been a long while since I got one... MSP is not giving out as many Prestige cars as before, it seems).

IIRC, I got a silver one which was loaded, everything-automatic (steering column adjustment, seats, windows). It had Sirius, and nicer, larger alloy wheels. I also got a white (almost cream) version that wasn't as nice: manual steering column adjustment is the one thing that stuck out as odd at the time. The wheels were not as fancy as the more recent rental.

Both cars had the Audi MMI interface, with the console-located knob to control options such as stereo, and a small LCD with all sorts of information. However, neither model had the built-in navigation system. Both cars had power foldable side mirrors, which is a great feature in tight parking spots.

One more odd thing I noticed about both cars: The Sirius radio seemed to be limited in the number of stations it could tune. I seem to recall I could only listen to one station per category...