They are saying a 6990 will draw 600W.  It is an ENTIRE SYSTEM including a pair of 6990 and other ultra high end overclocked components will draw 1200W total at the wall.

The system in the review is beyond foolish.  8GB of ram ultra-overclocked i7 CPU, massive hard drive, etc.  Even still it is 1200W @ the wall.  So at 85% efficiency (a guess) that is ~1000 DC watts (power supplies are always rated in DC wattage, AC wattage will be higher due to PS inefficiency).   How much of that 1K is due to the rest of system? Who knows.  The review is kinda useless.  If the system has 100% CPU bug and they didn't use affinity an overclocked i7 burning all cores @ 100% load can easily use 120W by itself.

If they wanted to do a real review they would record wattage of various cards on a usb linux key with no other components, measured at the wall, and they use power supply efficiency chart to figure actual DC load.  Take the system at idle (or single core @ 100% for 100% CPU bug) to figure actual draw of cards.