I am looking at 2013 A6 CPO cars. The things that I will miss if I don't buy a plus are the navigation and the back up camera. I am surprised that Audi wouldn't have these as standard, even on the entry level car. One salesman at an Audi store said those can be added, but they are not OEM. I am curious as to who makes them, how much, and how different they are from the OEM unit, or do they work with the same controls.