I'll second...or is that third...what Jody and Stuart said. If you want a SEMA quality car, I'll happily sell you a car that doesn't run and was put together in a thrash. That's the case for 60-70% of cars at SEMA. There are really nice cars at SEMA as well, but typically they weren't built specifically for SEMA. Many are just nice, independently funded projects that happen to be featured by companies at SEMA. Project Prodigy, Alumn8or, Inciner8or, Ricochet, and many of those caliber cars are what you're looking for I'm sure, but I wouldn't call them SEMA cars.
Good luck in your search though. I've got a ~600-700hp ProCharged Chevelle that might be up for sale. It was at SEMA '04 but has since been finished the right way. Still needs some things to make it perfect, but it's an impressive car. It really depends on what you're looking to spend as well.
Kris