mickeylex: Yeah, don't use NADA, that would be stupid. Buy the car, pay $10K more for it than book, then total it on day one, and then call me.
You should be safe paying roughly 3 to 5% more than NADA, for an NSX in great shape. Again, this is from an insurance perspective.
The guide, Mickeylex, you posted to is pretty good, but if you don't follow my rule of thumb, and jack your car, YOU WILL end upside down on your loan. Just because the market sustains, say 8% higher than the insurance companies evaluation, does not mean you will get that 8% back if you wreck the car. Granted, a 3% loss on 35k is roughly only $1,000, which most can fork over buying this type of car.
Also, you will have to fight your insurance company to get the extra 5% I mentioned above, as NADA isn't correct on these cars, and that is where their evaluation will likely come from (State Farm, Progressive, Geico, All State).
Do not use KBB as it is not even remotely close. I think for my 1993 it says it is worth $19,000, and the NADA value is around $32,500.