Not got an S3, but have a S Line Saloon which I believe has the same stock suspension.
I recently got the Eibach Pro kit fitted which lowers the car around 30mm I believe and H&R Spacers 12mm rear / 10mm front.
No issues going over speed bumps, no rubbing coming off my steep driveway - no issues whatsoever, it's been perfect - same with the spacers.
As for looks, the Pro kit is perfect.. just below stock height on my 19's, nothing crazy low or that looks obviously lowered it just sits "right".
The spacers push the wheels out nicely, I probably could have gone up a notch to 15mm/12mm, but I may have had issues, who knows...
Hope this helps!