alot of people have shy'd away from the Gs supercharger and went with the sts turbo kit, its cheaper and it makes more power, www.ststurbo.com , people have said that the customer service is horrible with them and that they are not getting the percieved horsepower that they say you will
The base STS system is good for up to 5-6 lbs of boost but to go higher you need an intercooler and/or methanol injection. The turbo on the base system is plenty capable in fact it is powerful enough to blow you stock block since it can only handle about 10 psi.
You can get a STS kit with the smt6 and front mount intercooler for about 5K and with that you can take it up to 9-10 psi on a stock block. I would also suggest a blow-off valve to releive back pressure to the turbo when you let off the gas and a boost controller so you can be in low(3.6psi) boost for daily driving then flip the switch and go to high(9-10psi) when you want more power. You can just get a 9-10psi wastegate spring but then you would always be at 9-10psi when going WOT.