750 but low quant - retake?

Retake from a 750? Are you insane?

Consider this: Last year Stanford dinged every single perfect score applicant that applied. What's the significance? Stanford doesn't care about score. If I were on the panel, I might vote to ding every single one just to make a statement: NO SCORE IS AN AUTOMATIC ADMIT.

If you retake, what message will you be sending admissions committees? You got a 750 first time around, 98% percentile. Meaning that you beat out all but 2% of the entire population ever to take the GMAT ("ever to take" works in theory). The AdCom will see your 750 first time take and then a retake that, if you improve is somewhere between 760 and 800. The 800 of course places you in a group of perfectionist, which would be reinforced by looking at your testing history and the adcoms will see First Attemp: 750, Second Attempt: 800. Schools don't want someone that is perfect, they want people that will be good classmates and strive for perfection while realizing that perfection is rarely achieved. There is always a ROI. You might write a 98% perfect paper and it takes you 6 hours to write it. Then to improve that paper from 98% perfect to 100% perfect takes you another 20 hours. Honestly, is this extra 20 hours worth the 2%? What was the return on your 20 hour investment? 0.1% per hour?

It's your decision, but my advice is to not ever take the GMAT again (as long as you apply within 5 years) because you will be sending the wrong message to the b-school adcoms. That message is that you are more interested in perfection that utility. Schools need someone that can someday go manage a company, not just take tests to perfection. No one gets 100% correct in a business environemnt for which you're being prepared during b-school.