I believe that has been talked about ad nauseum on here quite a long time ago. That was back when RSes were built to approach 300hp. What it came down to was a REALLY expensive build that might have had 300 crank, but never 300 wheel.
What is the reasoning? If you want that much power, there are plenty of cars nowadays that do that effortlessly. If that was what you were looking for, I would question the BRZ purchase.
With the newer direct injection engine, and the fact the RS thread would be much help for you, but I could scrounge it up.
- brian