Is my PSAT score good? How much higher should it be before I enter the National Merit Scholar Competition?

I just took a practice PSAT and scored it online. I received a 184. I know that this is pretty much synonymous with a 1840 SAT score. I'm happy with it because I'm 14. I took the SAT when I was 12 for a special program and scored a 1600, so I've made improvement. Do you think this score is good? How much higher should my score be before I enter the National Merit Competition, which requires a high PSAT score?