2000 Mustang V6 Tuning Question?

I was considering blowing my graduation money on the SCT Tuner on AmericanMuscle.com but im not sure if the tuner is really worth it. i know people say they felt a tremendous amount in hp/tr gains. But anyways i have 2000 mustang V6, its automatic and besides a CAI, Straight Pipes with Thrush Mufflers and new wheels and tires, the car is stock.. i dont want the worst tune and not the best, im just lookin for a mid grade tune ( i think thats the performance tune) and i want it run on 87-91 octane fuel.. So can anyone tell me how much performance gains i can get out of this?? and dont bullshit me with "just a buy a v8" **** bc my answer to you is i dont have enough damn money for insurance on a v8.. and besides my dad has a cobra, and that baby is mine on the weekends :) (pussy magnet ;) haha) thanks for the answers guys