I agree with the above, stage 1 is great, stage 3 is better, but stage 2 is kinda pointless if you ask me. If you want anything beyond stg 1 go the whole hog, get a bigger turbo and go stg 3 - or as Ruddmeister says, just go for stg 1 with ARBs and coilies and a weight reduction
It's so expensive to get that little bit more power that stage 2 is not really worth it, you can ditch the rear seats and spare wheel for free and it'll get you the same (well, similar) gains on the 1/4 mile!
If you've got money to burn, go BT