With AMD's Radeon HD 6990 stealing the performance crown only two short weeks ago, we knew it wouldn't be long before Nvidia answered the challenge. The company's GeForce GTX 590 was a poorly guarded secret, with specifications leaking as far back as last fall. Today marks the flagship's official launch and needless to say, we're excited to see how it stacks up to AMD's dual-GPU offering.Before slamming the GTX 590 with our battery of tests, we'd like to quickly recap our Radeon HD 6990 findings. Code-named Antilles, the AMD card is essentially a pair of Radeon HD 6970's fused together, albeit with lower GPU and memory clocks. Overall, it's roughly 6% slower than two 6970s in CrossFire. That deficit is compounded by the 6990's pricey $699 MSRP, higher thermals and louder operation.