The big black S6 was a wonderful, unique car, but only Audi enthusiasts recognized it for what it was. Great exhaust note. I loved the car, hated the transmission. It had the 6-speed ZF with the notorious rough 2-1 shifts. That, and a very touchy accelerator pedal, made it unpleasant to drive below 10 mph, as in heavy traffic. Above 10 mph, is was a dream! Fantastic car for a long, fast trip across the desert. Sold it at 52k miles.
The silver S5 was really a fun little car. 6 mt, adaptive suspension and sport differential, rpm matching and a great exhaust crackle made the back roads a joy. But it was a small car, hard (for me) to enter and exit and I felt a bit claustrophobic in it. No gravitas. Sold at 7k miles.
The S7, so far, is great. Nice size, elegant and fast. I like the HUD. I think faster than the S6. Great transmission. Otherwise very similar to the S6. I have had the display modified to include what gear the transmission is in. (D1-7 & S1-7). Boost gauge is next, probably a chip but I am concerned about the impact of a chip on the warranty.