The NB is the better car and the NA is the better Miata. The NC is a better car than both, but in stock form it's still not the best Miata. If the car is going to be a daily driver, I think I'd keep the NC, throw a set of Tein Flexes on it and call it a day.
However, I think the NB is a better Miata than the NC. If you're looking to keep that experience, then keep the NB, throw a set of Tein Flexes on it, bolt on a blower with the money you'll save in car payments, and call it a day.
Come to think of it... you should probably just keep the NB, blow five grand on Teins and a blower, save yourself the car payments, and call it a day. ;)
Good luck and Godspeed.
