From said arguments, the most logical thing to do would be to sell the SC kit and pay for a racing school and more seat time since the SC is too much for a new driver to handle. Taking that even further, sell the NSX and buy a spec miata since the NSX isn't as much of a "momentum" car as the SM, so you'll learn more from the SM than the NSX.
I disagree. A SC NSX is fine for a beginner as is a 911 GT3. The GT3 is as fast as the Koni Challenge cars I race, and its more than fast enough for anyone. I recently worked with someone new to tracking and I found it to be a great handling, good platform for him to learn on, and he enjoys exploring the limits of that car. Anyway, I'm not going to get into an ego contest in regards to the "instructor" comment or mean anything by my instructing statement other than it being an example of a newby with a much higher performing car. For the OP, keep the SC, it puts the NSX into a more competitive level to the power of modern sports cars.
I remember watching your in-car footage from Road America and effectively using your brakes will yield SECONDS per lap. Thus a racing school will be your best investment.
Since you wanted to buy something materialistic for your car (hey, everyone has the itch), while I am still a proponent of improving yourself as a driver before the car, I feel in terms of a part, the V3s and a better alignment will be the best option over the previously stated recommendations.
Billy
