I'm guessing you're up in JHB? If so I'd suggest going the S3 route, since the N/A cars just aren't able to really unleash their awesome power at the reef
When I was looking for a car I was choosing between the S3 and the 135i, and I must admit, the S is a truly awesome vehicle and the S-Tronic box is topline..but the difference in power took me on the 135i route.
At the end of it all, it boils down to what kind of drive you prefer.
Take Care dude, good luck