I'd suggest a GT30R. Pretty quick spool and makes as much power as you're looking for.

As far as kits go... call Main Stream. They built a 700hp S2000 w/ their own tubular manifold, V mount intercooler and more. I'd personally get it done locally with someone who has experience and in case anything ever happens... you've got someone local that knows the car.

You can look over dyno sheets, get a pretty accurate estimate, peace of mind of them being local and having it tuned at the same location.

Main Stream - 678.567.9384