sway bars: i don't know if the IPD is adj, if not, get the whiteline like i have, 18mm-20mm-22mm. get endlinks too.
+1 for the wheels too.
springs: depends your resources, if you have quite a bit available, get adjustible KYB AGX and some good springs. if not too much, get some KYB GR2s and some H&Rs or eibachs, etc, search for spring stuff, there's a ton of info on here about it.
engina: you're not gonna make any power there. all i can say is swap it if you want power.
if you're good with wires and have access to an auction, you're set. get a wrecked WRX or STi and start bolting it all in. it would be wisest to get a whole wrecked car, take out the engine and tranny, ecu and wiring harness, transplant them. (it all bolts up, no ****) put the rest of what you want on, and sell the sspare parts for the going rate and you'll have a very cheap 230hp (wrx stock swap) or not too bad of an STi swap. (300hp stock)
body work: scoops: read above. lights: read above.
all in all, sways and wheels and tires. best bang for the buck of them all.
the rest is all in how much you wanna spend.