I'm on my 5th S197 supercharger setup:
08 V6 with a Vortec base kit (SUPER easy install, loved it, shoulda kept it),
05 GT with a Procharger (what a frikkin beast, 595 rwhp - had hard miles on it when I got it, too much boost for the 4.6, blower had significant wear after about 40K when I pulled it out),
08 GT with a 2.9 Whipple (it had 110 lb/hr injectors, WAY too big, didn't want to run below 2000 rpm),
07 GT with a Roush 0.9l (closest to OE feel, seamless operation, blower was like new when I pulled it out with 39k miles on it),
07 GT with same 2.9 Whipple kit - gotta downsize those injectors!).
After all this, my advice is to make sure you REALLY love that car cuz you're gonna be way upside down in it.
I'd look for a used kit - not an easy find but they are out there, I've sold 3 of them - buyers got a great deal on complete setups. (Try searchtempest.com, racingjunk.com etc.).
Other than cost I gotta say the extra power will totally transform the car into something visceral and exciting - BUT you gotta upgrade suspension and brakes. The 07GT / Roush 0.9l had stock suspension and brakes when I got it and I was shocked at the bouncy, wallowing ride after 3 cars with upgraded suspension. (Good thing I already had the parts to upgrade it!)
I'd look very hard for another car that someone else has built up, you'd be surprised how cheap you can get one.