Typically, stage 1 = 280, stage 2 (rare) = 300ish, stage 3 = 330, but this varies between tuners.

Stage 3 involves quite a bit more boost, stage 1 is a nice improvement, with a good aftermarket exhaust. Not a huge amount of stress on the car, noticeable performance difference. Prob best bet if you are worries about breaking things...

Saying that, mine's stage 1 on 114,000 miles without an engine rebuild and still going very strong.