Graphics Upgrade, a few questions

Hey all this is my first post so here I go.

I currently have TWO Nvidia EVGA GTX 460 SE 1GB cards in SLI.

My main use for my computer is gaming. Games like Skyrim, Starcraft 2, Company of Heroes, Black Ops, Metro 2033, Bad Company 2, Brink.. just to name a few. Im thinking about getting Battlefield 3 and Modern Warfare 3.

I want to get a GTX 570. First question: Is it really that big of an upgrade? Im trying to get away from SLI as well.

Second Question: Which should I get?

ASUS
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

EVGA- Im a bit confused as to what the difference is between these two
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

So what do you guys think? Upgrade? and if so which card should I get. The minor price difference between them isnt a concern.

Other specs: i5 2500k @ 4.5 ghz
12 gb ram
850watt Corsair psu
Level 10 GT case
p8p67 pro motherboard

Thanks for your time.