yeah, if you want to get a very high quant score, I would second this on manhattan. the books don't actually take that much time to get through per book, and have a good amount of practice that is more challenging than the actual GRE. Also, if you're not that concerned with verbal, you could just buy the quant books you want and skip the others, there's no need to buy all 8. I think Manhattan also does a good job of covering content, not just test-taking tips and tricks.
I just took the GRE today after having studied with Manhattan, and got a 167Q. I recognize you may want to score a couple of points higher, but I don't have a maths background and I felt pretty well prepared.
