I think with the 2.0 engine you'll see close to the same HP, but less torque. HP and torque numbers will probably be similar with the 2.0. The 2.5 engine just puts down more torque. I think you'll be happy. Don't drive abusively and the drivetrain should be fine. No hard launches or power shifts.
Also, if you haven't planned it already, you'll need an UpPipe and Turbo Back Exhaust. An STi TMIC would also be a good idea (any year will fit, 04-07).