i would suggest you get a set of quality components like (in no particular order) h&r, eibach, neuspeed, ground control, etc, and some good shocks to match. i would also suggest you do no larger than 16" for wheels, but it sounds like you already have the 17".

now, it'd help to know what you're looking for in suspension upgrades. also, do a search. there are countless topics on it.