You mention "MFE PHD", which is a bit confusing, because it is not clear whether you are seeking to enter a Masters degree program or a Doctoral program. These really are quite different, as the former is a professional degree designed to get you a good job in industry, while the latter is a research degree intended for those who plan on academic careers.
As for the Ph.D., the general GRE quantitative test does not measure very much as far as the math that you will really need in a quantitative doctoral progam. If you want to demonstrate your expertise in this area, you should consider the GRE math subject exam (which is offered at paper sittings only a handful of times per year.)
Also, as you may already be aware, you only have a couple more months to satisfy your dream to get an 800 Q score on the GRE general test, as the exam format is changing from August 1st. The new scoring scale will be 130-170 in 1-point increments (in contrast to the familiar 200-800 scale in 10-point increments.) Note that if you do sign up to take this new version during August or September, you will only be charged 1/2 of the usual fee, but your scores will not be made available until sometime in November.