Here's a scenario that shows how good it can be:
AU2 XR8 200kW base
Herrod Stroker Kit, Basic 275kW $6500
Herrod Valvetrain Upgrade $1500
Herrod Stud Girdle $600
Herrod GT40 Upper Intake Manifold $800
Herrod Manifold Spacer $120
Herrod 75mm Throttle Body $675
Total $10,195 for an easy, reliable 330kW with full warranty coverage. And don't forget the torque from a stroker...

:CraZ:
Go further if you want by doing exhaust and other bolt-ons when you get used to the power!