best dollar per horse upgrade is the cam. Might I suggest you look in the supporting vendors section? Several very good companies there, including 402 motoring, HHP, PPP, ProMotion Tuning, and Tbyrne (listed in alphabetical order to protect the innocent)
The Frank's Cams are very very nice (Sidewinder, Tomahawks) as are comp cams, and others which Iknow less about. Feel free to talk to the vendors, seek their advice, and see what other forum members have to say about their own experiences.
Get rid of those stock cats that are choking your exhaust. Either a good set of longtube headers with high-flow cats, or if you plan to stay with the stock exhaust manifolds or shorty headers, get some JBA catted mid-pipes.
If you plan to eventually do heads or cam swap, you need headers and high-flow cats (or no cats) to get the most out of those upgrades. If you don't see yourself doing heads and cam, the stock cats and exhaust manifold are still probably the next power robbing parts you want to address