Again mate to the best of my knowledge joining the cards together is supposed to give you a better res and lessen the strain on say a single card. So why the temps are different is something I think we had better ask one of the graphics people if that is ok with you?

That is not to say I don't know how they work but not being a gamer am not familiar with the machinations of a two card set up.

Myself I would say run each card separately and see what a test on each comes up and I think form memory they usually suggest the Furmark test.

Sorry this is dragging out and I must say you have been very patient unlike some - but it is fixable I am sure.
John:)