I went with the X-Charger kit from Explorer Express. Great kit, came with absolutly everything I needed to install it.
This kit differs from the Vortech/Procharger kit in that it is a twin screw SC instead of a Centi. From what I've read, the twin screw is better for daily driven cars because it makes boost at lower RPM's. Centi's make it up higher and make more power but is more for the hardcore.
Personally I like the look of the X-Charger better, and it looks almost like it came like that from the factory. Fit and finish are great.
The power is nice, the 3.0 pulley on the X puts out 6 psi and the 2.8 pulley makes 9-10psi.
Bottom line: All three of the kits are great, you just gotta figure out what you are gonna do with your car.