dual loop. if your going to have that much dissipation and your obviously wanting to overclock very high then you will want the second pump. thats beastly though. im just looking to do a xspc ax120 on the cpu and a ax240 on the gpu since i want to squeeze all this into a mini-itx case. although im in the same boat as id like to save the space with a single pump/res combo but its likely only going to allow for modest overclocks. but it sounds like space wont be an issue for you since you will have "two" 480s.