It is difficult to buy an NSX this way. Many people spend over a year looking for the car that they want. It can be extremely difficult to find the color, mileage and condition that you want with these cars.
My advice, once you find the NSX that you want, if you still have your Subaru, blow it out. The difference between wholesaling your car and selling it privately is no where near worth giving up the NSX that you want. Plus, if you finally sell your Subaru privately and the NSX that you want is gone, you're going to be paying MORE to get a good car quickly.