While I can't speak to the significance of being a National Merit Scholar in the application process, I can say that you should study for the PSAT either way; there's a strong correlation between those who perform well on the PSAT and those who perform well on the SAT/ACT. Additionally, although money one may be awarded as part of a scholarship will not be used to cover the cost of room, board, or tuition at one of the academies, I have been informed by an admissions representative that USNA allows entering midshipmen to use any scholarship money they have received to be put towards their other expenses and see a little more of their monthly stipend. Hope this helps.