That's a pretty tight timeframe.
What's more important to you: taking the test in 6 weeks or getting the 670-680? You might be able to do both but, if you can't, which one takes precedence?
I'm asking because a lot of people just want to get the test over with, so they pick an arbitrary date and decide they're going to have this score by that date. You can't really decide that though - this thing will go at the pace it's going to go and you can't really force it. :)
You mention now having the quant and CR guides. What about RC? Are you already doing well in that area and don't feel you need any help? If you do think you have room for improvement on RC, how are you going to do it?
The verbal section is not worth more than the quant (not really). The scoring scales just aren't quite the same, that's all. It's confusing because they look like they should be on the same scale. They're just not.
As a general rule, the higher you go, the harder it is to go even higher. In other words, no, you shouldn't plan to gain your improvement mostly in verbal. Look for improvement in both. At the level you're at, you want to try to gain 15 to 20 percentile points in both sections (so your verbal will still be higher than quant in the end).
I just saw your last paragraph. Okay... you are probably going to need more than 6 weeks to get to your goal, given your schedule.
First, school grades are the priority - once they're on your transcript, they're locked in forever.
Second, I assume you're not applying this fall because most b-schools require at least 2 years' experience. So that means you probably don't have to take it now - you just want to get it over with. Is that right? Tell me if I'm wrong!
Next, what to do? First, read these:
https://www.manhattangmat.com/blog/inde ... lly-tests/http://www.manhattangmat.com/blog/index ... -the-gmat/Second, keeping that information in mind, use the below to analyze your most recent MGMAT CAT(s):
http://www.manhattangmat.com/blog/index ... ice-tests/Then come back here and tell us the results of your analysis, where you think you fell short and why, and what you think you need to do to get better. We'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze everything - figure out what the data means and what you think you should do about it!)