Hi alldet11111,
First off, a 650 is a solid score (it's right around the 80th percentile overall) and it might be enough to get you into Business School. Based on your prior practice scores, it's understandable why you might want to retest, but it might not be necessary.
Before I offer any advice, I'd like to know a bit more about your prior studies:
1) How long did you study?
2) Did you use any other resources besides the
MGMAT Course?
3) When you took your CATs, did you take the ENTIRE CAT each time (including the Essay and IR sections)?
Given your Official Score, I agree that focusing on the Quant section would be a good idea. How much time do you think you would be able to commit to your studies each week?
GMAT assassins aren't born, they're made,
Rich