Yep it's a dual 5970 setup. It's a power hog too needing about 550 watts just for the card. I would go with a 750w PSU minimum. Stick with Corsair, Seasonic, PC Power and Cooling, XFX, Silverstone, Enermax, OCZ, Antec or the higher efficiency Rosewill units for quality.
550w to 600w for one HD5970 , If going dual you NEED 800w
That are huge cards, run hot and are very loud
And a single HD5970 is somewhere between a 7950 and 7970 for performance (depending on game and features used)
The 5990 is a dual 5970 card. It holds the title of the most power hungry card ever. Like I said a quality 750w power supply minimum. I would probably go with 800 watts or hell if the card uses 550 watts all by it's self 900 watts is not crazy especially if you are overclocking.
Just to clarify the 5000 series had a slightly different numbering system
The single GPU top end card was the HD5870
The Dual Card is the HD5970
Anything with the title of the HD5990 was just a modified (overclocked or more memory) HD5970
As a previous owner of 2x HD5970 (2x dual gpu card, so quad fire setup) 800w is the bare min to run 2 of those cards without overclocking
IT was the most powerhungry card ever made as also was the longest length card with a stock cooler made (i know 3rd party coolers can be longer on some card)
at 310mm length