Build advice

Hey guys im looking to retrofit my 6 year old gaming PC here soon, and by retrofit I mean totally rebuild it. here is my current build:

AMD Phenom II X6 1075T 3.00Mhz
6gb DDR3 RAM
Nvidia GTX 470

my question is this, I am really not having too many issues with frame rates yet even on the brand new games so I was wondering if upgrading to SLI on the GTX470's would be comparable to upgrading to a GTX 970? Thanks for the help guys
 
Okay well from that benchmark I would just be better off getting a 970 as 2 470's wouldnt quite have the power...
 
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