I dont know what gpu I should get for my build. I have a amd 8320 and a asus tuf board. Ive been thinking about getting the 4gb 770 then sli it later then I realized a single 780 ti is less expensive then 2 770 4gbs or I could get a 770 2gb and sli it later but idk if it has enough power by its self for ultra at 1080p. Someone help please..