Have you considered the Inno3D iChiLL GTX 670 HerculeZ 3000 Edition?
A mouthful of a name I know. Despite it not being available in many places, as far as I can see it's the best GTx 670 around. Period.
It's load temp smashes the Palit JetStream by 19 degrees, hitting 59. It's cool, it's performance beats or matches a GTX 680 and it's just £340!
EDIT: I apologise, in my quick enthusiasm for this card I failed to read that you wanted to water cool the card later, where the amazing air cooling of this card would become moot.