Just debadge them, and 99% of people won't know that you have the high end version.
Audi S line is kinda good too, but they really dropped the ball this generation. The S4/S5 are barely making enough power to compete with the 335i. The upcoming RS5 should fix that, but Audi is probably going to charge so much for those, that the $60K M3 will look like a bargain by comparison.
The S4 and new S5 are v6, which means they probably aren't as painful on the mileage. This is the biggest reason not to get an M.