With these settings that i posted power draw from the wall is 665w with Corsair AX1200.
In the past i was haved 4x5970 on this power supply without problem.
I don't know why your UPS screaming.
My cores on the cards in the moment is 808mh.
Anyway 1500kh is perfect for your configuration.
i downgrade core clock to 808 as your setup.
im running two 5970s with one psu 750w i think this should be enought for two 5970s?
i lowered fan to %70 and ups stopped alarming.
one last question.
what is your memory clock and voltage?