Cat back system? Get a decat and manifold. You should feel a small difference.
Brakes wise i'd go for a 266mm set up from a 206 gti. Should be able to get the calipers and discs cheap enough. What wheels have you got?
Suspension wise check out the Kam Racing website. Quite a few deals. Most people like blisteins (sp) with Faulkner springs but that's quite pricey. A spax kit should be fine. Even a spring kit with the torsion bar set to match would be ok, just not as good a ride