400-600. Get one that has already been converted for US use. Canepa's 959's make over 600 hp, and have modern turbos instead of a sequential dated turbo system. They have been fully federalized with bumper, and door adjustments too.
Why do people love it?
It was the CGT of it's time. A technological wonder. A 997 Turbo is more advanced, and faster than original 959's, but isn't as special. Not the heritage. A good "cheap" supercar to get would be XJ220's