Springs and swar bars will definately improve your handling. I know a lot of people go all out and get new coilovers. Not really sure why when most people dont really race at the track.
Intake will be a good choice as well. Easy to install, sounds nice, give you a little power. Not too too expensive either.
Depends on your goals really. If you want maximum power for your buck . . . downpipe. If you want handling . . . springs / rsb. If you want a little power and a cool noise . . . CAI.
Just read any review about any brand CAI. They are all pretty similar and should all work fine.