I've tried EX-P+ over NXT on my dark blue paint and I didn't like it much. #16 looks much better and might actually be more durable.
However, since your paint is so much lighter than mine, why not try EX-P topped with Natty's. If you wanna stick with NXT, then top with #16, but I would go with 2 or 3 coats of NXT first.