sct x3
I have one for my 07 scab. IMO, it's worth the money if you use custom tunes. You might want to add a better flowing exhaust and intake as well. If you don't mind waiting for your tunes, go with Troyer. If you want them right away, Mike at 5 Star is good as well.
Bill and Corey at powerhungryperformance.com also write custom tunes for the X3. Another tuner to look at if you are going with custom tunes is the gryphon or the gryphon CS/CTS (only at PHP though). I went with the gryphon from PHP and it was worth the money, as would the X3.

