i had an antec 500 basiq, i had easily 750 running through it. 2 8800's plus a quad core and 2 water pumps. antec is a power house for sure. a little noisy under load though.
I have a single rail ultra lsx single rail now. only bought it for the sli power draw of 2 460's.
As for the Ultra, congrats on getting a mediocre half-bridge Andyson 600W unit from 2004.