I am going to be building a gaming PC soon but I'm not sure what to get. Its either the EVGA 025-P3-1579-AR GeForce GTX 570 (Fermi) HD 2560MB 320-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card (link http://www.newegg.com/Product/Product.aspx?Item=N82E16814130687), or 2 EVGA 02G-P3-1559-KR GeForce GTX 550 Ti (Fermi) 2GB 192-bit GDDR5 PCI Express 2.0 x16 HDCP Ready SLI Support Video Card (link http://www.newegg.com/Product/Product.aspx?Item=N82E16814130652). Which should i get 2 gtx550ti or 1 gtx570.