if you can get above 700, a good essay can get you in top 15 VERY EASILY
if you can get above 680, work hard on your essay, top 15 is totally reachable
if you stay put, well, you MAY still get in.
Your background is pretty strong. Your GMAT score is, however, a shame. My suggestion is for you to write the test again to ensure you a top 10 school. If you really want to have a try without the renewed score, you had better to cook your essays very well and to conduct the on-campus interviews of your target schools. Good luck.