A decent CAI & tune combo is roughly $600-$650. Go to the Brenspeed and Bamachips websites. They're 2 of the preferred tuners. Their tunes are more aggressive and perform better than the canned tunes you'll get from "other" vendors. The CAI & tune is probably the biggest bang-for-the-buck short of going FI.
Other power adders would be LT headers and O/R X pipe, UDP's, CMCV delete plates... Stay away from aftermarket TB's as they don't add anything over the decent stock TB.
You might also want to consider an aluminum 1 piece driveshaft and other "weight loss" mods.