I am currently running dual GTX 460's and one of them is shitting the bed so I want to upgrade. I was looking at the GTX 680 but I notice on amazon that the GTX 7 series are cheaper. Any help is appreciated, I'm a noob when it comes to pcs. Also my rig is a custom Alienware Area 51 PC. (I know now, I should have built my own) my power supply is 650 watts if that helps. Thanks!