It should. It's a tier 3 PSU. http://www.eggxpert.com/forums/thread/323050.aspx
Not the best, but good enough. Each HD 7990 is a 250W card maxed out. That's 21A on the +12V rail for each card at max. 63A just for the 3 cards alone. You'll find out how good the PSU is built, that's for sure. If you don't trip a circuit breaker.