Don't forget the GMAT is a means to an end, and therefore whether or not you should retake the test depends on which B-school you are targeting. 670 is good enough for you to get into most tier 2 programs, but if you are targeting the top tier, you will need to re-write. With your strong verbal aptitude it's likely that you will improve your score significantly.
If you're not sure which school you want to apply to and you have time, re-writing would be a good idea because a better score will give you more options and a greater chance for acceptance.
In my situation, I studied, wrote the test, and scored a 660. I knew I could have done better (based on practice tests and knowing that I had missed problems that I could have got), but the school I was targeting in Canada admitted an average GMAT below what I had scored. So instead of re-writing the test I turned my attention to the remainder of the application and in particular towards submitting my application as early as possible. It worked out and I was admitted.
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