Sorry for the long delay in replying to your message. It is difficult to say which schools you should apply to without knowing your full profile and research interests. However, if you want to get in somewhere in the top 20, you should try retaking the GRE for the score closer of 780 or better (aim for 800). A score of 750 is probably okay for schools ranked below 30th or so, but a lot depends on the other aspects of your profile.