A month ago I had a Vortech installed to my 2000 GT 5sp with 8-10 lbs of boost. For $3800 it included installation, K&N air system, 30 lb fuel injectors, new chip, custom tuned by the speed shop I had it installed at, plus a million other parts I can't remember (you can get the full parts listing on the Vortech website if you want //www.vortechsuperchargers.com). I did not have the intercooler installed, which it sounds like you want. I asked the speed shop about adding the intercooler and they said its not really needed on a Vortech until you start pushing over 10 to 12 psi. You mention you don't want to install a new computer chip or reprogram the existing one. I'm not a hard core gearhead, but I don't know how you could get away with not haveing a new chip, or reprogramminging the existing one. Adding a supercharger is a serious mod and without the computer knowing about its addition I would think you could seriously hurt your engine and/or not get the most out of your SC. I've had my Vortech over a month now and love it! No problems and great power! You might want to check out this website for more info on superchargers. They're a bit Vortech biased, but for good reason.
http://www.motorsportsdigest.com/tech.htm Good luck!