a ~20mm rear swaybar goes along way in making the car handle better. Also, do tires. the scoob responds very well to good rubber. after that, it depends on $$$, how harsh you're willing to put up with, and driving conditions. On the cheaper side of things is STi suspension (IIRC you have to buy it used now, but still very very nice). Another cheap route is KYB AGX struts and Eibach springs. You can also then get the Ground Control threaded collars for adjusting ride hight. There is also the Prodrive setup which is very nice as well. Above that in the money range is Tien and Leda Coilovers. I've never been in a car with these. Top dollar is DMS. They have a 40mm coilover that's not too expensive for the street. If you plan on racing, espeacially on a loose surface, the 50mm is the way to go. Very trick, but you pay for it. And then the ultimate, if you happen to have ~$25k to spend per corner, is the Olins Group A suspension

That is obviously rally only.