1x with one, 2x with two, 2.8x with 3. Noticeable,somewhat, for the price your probably better off with 1 card then 3, and two might just be bread and butter, but 3 is definitely bragging rights. Yet i heard 3 280's at max resolution at 2560 by 1600 max settings all on very high still could not run crysis, ran at 20fps. So worth the gains, possibly in other games a slight gain.