stock GTI driveshafts how much power?

How much power can standard driveshafts take? and whats a good up grade?

Definitely more than around 170-180bhp. If you need an upgrade, go to 100mm CVJs. These will take loads, possibly 300bhp or more. Its not just the power, its the weight of the car too which will make a difference, ie the torque applied through the wheels. Basically, unless you're on slicks on Santa Pod raceway, you'll probably spin the wheels rather than break a transmission component.

is that both inner and outer cv's need to be changed or just th outers? as on mine i can't change the inners with the engine set up i have
what sort of torque will the std ones take?

With cabrio / Scirocco 100mm innners, there literally nothing to worry about for road and track use under 350/400 bhp, and possibly more.

It's the box that goes first.