That motherboard is over-priced for what you wanna do; unless you are going for quad sli.
GIGABYTE GA-990FXA-UD3 AM3+ AMD 990FX - $149.99http://www.newegg.com/Product/Product.aspx?Item=N82E16813128514
Saves you some cash. Also, upgrading from the 7850 to 670 would not be worth it. You would get a slight performance bump but you'd be spending $400 more.
With the money saved from the mobo get this Hard drive instead:
Western Digital WD Black 1 TB - $104.99http://www.newegg.com/Product/Product.aspx?Item=N82E16822136533
more space, much more reliable.