Don't worry about the Turbo sizes. Believe it or not, its the compression ratio that you want to delve into. Thats all science though, so don't worry too much about it.
Check out this site for the most popular turbo kits. It lacks the Greddy Turbo, but it won't ask you to keep it off the streets or to use a cat-delete (not carb legal).
Definitely, go with Stage 1 or greater though. Not having a Blow off valve or intercooler has its consequences.
www.turbokits.com
www.treadstoneperformance.com