There's not a whole lot of point wasting money on aftermarket pads,if you're after better braking all round.
The S3 brakes are heavy(weight wise) and prone to fade quite quickly,trying to stop 1500kgs of car.
If you want something better,invest in a decent brake kit,either from DaveB1970,or APRacing,Brembo etc,or maybe an RS brake kit.....all of these will be vastly better than something like a more aggressive set of pads.
Mine are a hybrid of VWRacing's 6 pot calipers,with AP rotors,and Mintex 1155 pads,although those pads are more track oriented.