@ OP - Best Graphics card varies from user to user depending upon the applications. What will you try to do with Graphics card. Also as Willdobbo suggested GTX 660 / 660 Ti might be the highest range of graphics card your processor wil run without bottleneck
There isn't really a "best" graphics card for your processor it all depends on that you want to do, but so you don't get bottlenecked I would suggest something like a GTX660 or a GTX650TI Boost, Card around that range
@ OP - Best Graphics card varies from user to user depending upon the applications. What will you try to do with Graphics card. Also as Willdobbo suggested GTX 660 / 660 Ti might be the highest range of graphics card your processor wil run without bottleneck