Turbo suggestion

500-550HP should be easy. I'm using the GT45 but I like the 7875 at VSRacing. They have a cast and a billet wheel model for a little more money.
Another factor to keep in mind is the weight. The GT45 is an awesome turbo for the price but weighs around 37 lbs. The 7875 is 22. Makes a big difference when building your hotside.