Hi jarbit,
Your original 510 was a solid initial CAT score (the average score on the Official GMAT hovers around 550 most years). If that Score is several months old at this point, then we have no idea what your current 'ability level' is; as such, you should plan to take a NEW, FULL-LENGTH CAT sometime soon (perhaps this weekend. Make sure to take it in a realistic fashion (take the FULL CAT - with the Essay and IR sections, at the same time of day as when you'll take the Official GMAT, if you'll be at a Test Center, then wear a face mask, etc.). Once you have that score, you should report back here and we can discuss the results and how you might best proceed with your studies.
Before I can offer you any additional advice, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) What type of study routine have you been following? How many hours do you typically study each week?
2) Have you used any other study materials besides the ones you mentioned?
Goals:
3) Is your overall goal score 720 or something else?
4) When are you planning to apply to Business School and what Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich