very nice work!
The projection of 500HP with new turbos is not ridiculous as even without new turbos, with RACEGAS tune & full bolt-ons, N54s have made 440rwhp+. (517 BHP)
However, for maximum power, if you supercharge your M3 V8 with something like ESS VT2-625 or Gintani Stg 2+, you will be able to achieve 560-600WHP on 91-93 pump gas (650-700BHP). This is where you will be able to beat most supercars in straight line performance, & trap 130MPH+!