I traded my 2011 Audi S4 Prestige with drive Select on a 2013 S6 with the invovation package. Although the S6 was 30% more expensive than the S4, I consider it a bargain. It rides better, handles better, is faster, and is techincally much more advanced than the S4. It also gets just as good gas mileage. I have been driving Audi Quattros since 1987 and This is my eleventh one, so I do have considerable experience with the brand and know what I am saying when I say the 2013 Audi S6 is one awesome car.
Prestige quattro 4dr Sedan AWD (4.0L 8cyl Turbo 7AM)
I purchased this car with approximately 40,000 miles on it and by 60,000 it needed over $4,000 dollars in repairs. At 50,000 miles the "check coolant" message appeared every day until a visit to the dealer revealed that a new water pump was needed at around $2,000 with labor. Not 5,000 miles later the engine developed a high pitch squeal at idle. The remedy for that was a costly repair to the high pressure oil system. Throughout the ownership of the car a clunking noise could be heard from the passenger footwell over every bump. This was never actually solved but was believed to be the front drive shaft and was replaced. Granted the dealership sympathized with me over the problems I was having and had Audi cover the cost. The adaptive cruise control went out of calibration several times and disabled the cruise until a $400 calibration was completed. Besides from the mechanical issues several interior rattles showed up in quick succession. Maintenance costs were as expected for oil changes but in order to perform the 75,000 mile service the entire front end would have had to be disassembled adding up to a $2,000 plus charge. All that aside the car itself was fantastic. The engine sounded rich and the acceleration was insane. The interior looked premium and the quilted seats were gorgeous. The exterior of the car had just the right blend of sport and luxury. All in all the dealer was exceptional and I would recommend the car if you don't mind the high maintenance and repair costs.