This is really a difficult question to answer, because it depends on how much effort you think will be required to break 700. If you do choose to re-take the GMAT, you need to take some time off for relaxation first. Go have some fun! As others have cited from experience, like jallen, you should try a new strategy this time around (if you retake).
Here's another idea that might be of interest to you though. Rather than increasing your GMAT score, have you considered taking on a fun new project? Maybe a small/inexpensive start-up? Maybe organize a new group in your community? A fun extracurricular that you actually WANT to do, could really strengthen your application. There's gotta be something that you would enjoy more than studying for the GMAT again. Share your ideas if you come up with anything, because I'm hoping to take on a fun new project myself

Congrats on the 670! That's gotta feel great compared to where you started!