I'd suggest you drive one first because they drive nothing like a BMW due to the over light and numb steering feel. I had a 2.0T Quattro and it was £270 a year to tax and only got 28mpg. More on a run. Build quality is good, but Audi's just seem so boring.
Also the ride on mine (s-line) was rock hard, very fidgety so the S3 would be even worse as it 10mm lower again. Boot is shallow too due to the Hadlex and diff.