Alienware X51 R1 Graphics Card Upgrade Question

The Geforce GTX 555 on my X51 R1 is starting to show its age. I was thinking about upgrading to an Asus Geforce GTX 670 2GB DDR5 DCII. Can the X51 handle this card? I already have the 330W PSU.

Any graphics card upgrade recommendations in general are also welcome.