a 6790 isnt much off from the 6850. 20 bucks cheaper or more. Look at the specs yourself. Now a 6770 or under is not 256bit.
Then personally Id ditch the vengeance. Then get atleast 6gigs of ram. Id lean more on 8. Which would end up same price.
Then Ive been eyeballing this for cooling http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Just makes sense to have a turbine engine design. That 212 can attach another fan, sure. But it does spin in opposite direction. To create a turbine on the sunbeam. Plus i like manual fan controllers. This comes with one.
Thats my personal opinion. Your setup is fine. Id just would really push 6gb min for the ram.
BF3 is currently eating all of my 4gb of ram for a snack.