The first mod to improve handling is to fit a Rallye rear anti roll bar, this gets rid of all the understeer and gives neutral handling.
For stiffer front springs try the Golf 3 VR6 ones, they are fitted to mine and they work very well.
For stiffer rear springs I have 11mm Dia H&R Passat 35i items with 2 coils chopped off, (the VR6 rear springs are to stiff at 12mm diameter) while the std Golf Syncro rear springs are only 10mm diameter.
For Shock absorbers I have Koni reds set to 75% hard all round.