Because muh ultra 16x AA
I have two 650s running two monitors, and can run almost everything decently well. 960 is much better, and there's no need to be wasteful if you have another PCI-E slot on your motherboard, so my suggestion is to get a second one instead. Save some money that way, and get a phone, too. Sure, it might not be too of the line, but this is how you get more for less money.