just put a pioneer avic-4000 nex in my all road, love it!. Some advice, ENFIG is the ONLY way to go for wiring adaptors but I would not buy the double-din mounting dash kit they offer. I bought one and had a few issues. It does fit but color match is horrible, its gray, not black and rubberized so if you scratch it, and you will, it looks bad. It also wouldn't allow the screen to open without interfering and because its rubberized sanding makes it look like crap. I had to have the unit out about 1/2" so it would open, a waist of $50-. I ended up buying the metra kit on amazon for $20-, one made for the a6. Fit/color match is excellent and with a little sanding on the inside edges of trim plate the unit opens and closes fine.
One more thing, due to can-bus I lost the ability to have radio on with key out in my car, radio is only on when ignition is on now. May not be a problem in newer models?