Hi tarun1vashisth,
First off, a 660/Q49 is a strong score (it's right around the 80th percentile overall), so it could be enough to get you into the PhD Programs that you're considering. PhD Programs tend to be rather competitive, since there are often a number of high-quality applicants for a relatively small number of 'spots.' As such, you really have to make sure that your OVERALL application is strong. You're ultimately asking Admissions questions, so you would likely find it beneficial to speak with an Admissions Expert about your overall profile. There's a Forum full of them here:
ask-admission-consultants-124/GMAT assassins aren't born, they're made,
Rich