I <3 microcenter but newegg is general cheaper. I faced this same decision i went with the 6950 1gb in the end. http://www.newegg.com/Product/Product.aspx?Item=N82E16814150527&cm_re=6950-_-14-150-527-_-Product
there are cheaper ones though.
i found that generally the card depended on the game but most slipped in the 6950's favor more so when unlocked if u get the 2gb. but at your res im sure both will be just fine for about any game max settings. so really like youll find everywhere else it comes down to preference. and to do sli/xfire u just need a mobo that supports it a good psu 750w or 800w maybe and thats abt it