Even though I mod pretty much all my cars, usually, when I buy a car I look for ones that have been generally left stock. In the case of your S6, I would buy that one in a second, if I was in the market.
The first mod I did to my S6 when I got it, was to install H&R coilovers, which cost me close to $2k with labor. If the guy purchased those KW v3 new, then it would have been almost double that. So, you can consider that thousands saved.
The stock wheels look great, but are boat anchors. Those wheels you have are OEM and forged. So, another upgrade. If you dont like them, you can sell them for more than you would have got for the stock ones.
And the res delete is another good mod, IMHO. With the current v10 S6 aftermarket exhaust offerings, the res delete makes a lot of sense to me, if all you want is increased sound. Perfect low-cost mod, until a better exhaust hits the market (coming soon)
Painted calipers look fine, and Im on the fence regarding the rear light tinting. Anyway, an easy mod to reverse if you dont like it.
The car looks well taken care of, and the fact that it has a recent carbon clean supports that. The guys dropping $3k on coilovers usually have money to keep their car well maintained.