The 460 is much like the 560 non ti. 560 in a lot of ways just an OC 460. 560>550ti. Given that you have 460 in SLI I would bet that you would need a gtx 570/gtx 480/7850 or better to be worth the upgrade only b/c those cards have more gpu ram for max AA. Other wise, w/o AA, you are close to a gtx 580.
page memory has nothing to do with ram -^. Its the virtual memory created on your HDD by windows. Usualy Windows sets the Pagefile to double the ammount of ram you have. But if somehow you have set your pagefile manualy then some programs might be "upset" that they dont have enaugh pagefile.