That really depends on where you are looking to apply. A 650 score is probably quite reasonable for places like Georgetown for example. Also depends on your GPA - if its low, you need to compensate with your GMAT.
School & Average GMAT
Northwestern 700
Chicago 695
Wharton (Philadelphia, PA) 716
Stanford (California) 711
Harvard (Boston) 707
Michigan (Ann Arbor) 692
Cornell (Ithaca) 673
Columbia (New York) 706
MIT (Cambridge, MA) 697
Dartmouth (Hanover, NH) 704
Duke (Durham, NC) 707
Virginia (Charlottesville, VA) 680
NYU 700
UCLA 705
CMU (Pittsburgh, PA) 691
UNC (Chapel Hill, NC) 652
UC Berkeley 701
Indiana 644
Texas - Austin 670
Emory (Atlanta, GA) 680
Purdue (Lafayete, IN) 667
Yale (New Haven, CT) 696
Washington U (St Louis, MO) 649
Notre Dame (Notre Dame, IN) 657
Georgetown 660
Where are you looking to apply?