I don't know witch to get i have see good things about them both.
HD 6870
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102948
HD 7770
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102968
HD 6870
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102948
HD 7770
http://www.newegg.com/Product/Product.aspx?Item=N82E16814102968