Which GMAT books are the best for scoring high on the quantitative section?

I’m preparing to retake the GMAT to improve my quantitative score. Although my original score wasn’t bad, I desire a higher score in order to impress the admissions department of the highly quantitative Ph.D. program to which I plan to apply this winter. On my first attempt at the exam, I used the Princeton Review book “Cracking the GMAT” as well as “The Official Guide,” written by the makers of the GMAT. Although these books were helpful, I don’t feel that they adequately prepared me for the more challenging questions on the quantitative portion. I already know the basics so now I’d like to find a book that specializes in difficult questions so that I can achieve a high quantitative score. So far, I’m considering “Kaplan 800,” “Turbocharge You GMAT – Math Study/Solutions Guides” by Manhattan Review, and “Project GMAT – Advanced Math” by Veritas. Any suggestions?

Thanks for your advice! 🙂