Turbo'ing a Jeep is impractical for a few reasons. Firstly, just because you throw some boost in there, doesn't mean you're going to be fast. You're not taking into consideration that your Jeep is geared pretty low. Secondly, if you want to do off-roading, a turbo may be counterproductive because of unwanted tire spin in mud or slippery rocks, etc. A supercharger may be a better route to take, but again it has similar negatives. Not to mention that a custom turbo set up is going to be expensive. If you want to go fast, get an import and modify that. If you want some extra ponies oout of your Jeep, I'd say; intake, header, exhaust, and a tune would probably do you just fine. Maybe a stroker if your real serious.
Just my $0.02