Im in college too so i know how you feel man. A turbo would rock but the only reason i would suggest not getting one is that any charger is gonna be high maintanence. If your strapped for cash, your car probably won't get the maintenence it needs with a turbo.
$600 won't do much for you if you go show. yeah you could buy a body kit, but that alone costs 600$. Then you have to get it painted. unless you somehow find an amazing deal, which if it were me i wouldn't want to wait around for a deal THAT good.
Since you've already got exhaust, i'd work on the suspension. You could do a decent amount of upgrading on suspension with $600. Springs, strut/sway bars, and/or shocks. I'm in the process of researching suspension stuff myself. You could easily lower your car and get at least a rear itr sway bar (assuming your not in a type r already) and have money left over.
Or hell, get a kickass system. one can't go wrong with a good system imo.