i think that if you were going to watercool any aspect of the pc, the priority would really be the processor. the gpu's don't allow a crazy amount of headroom for overclocking anyway, and the fans that are on them should manage to keep them relatively cool. if you plan on overclocking though, the processor is where the action is gonna happen and that is where the watercooling will be most important... imho you should probably start there and move on to the cards afterwards - thats just my opinion though lol, and its a nice build i must say - LOVE the processor!