The motherboard supports Dual Channel memory so it would be better to use a 2X4GB kit rather than a single 8GB stick.
CORSAIR Vengeance 8GB (2 x 4GB)http://www.newegg.com/Product/Product.aspx?Item=N82E16820233180
The GPU vendors use the same reference design but might make slight changes to the cooling method. Basically, they are just different brand names. For example, the brand of tobacco that someone smokes.