What is the most powerful PC desktop video card currently in the market?

More specifically, which chip? the nVidia GTX 590, GTX 295 or some ATI ones? Thank you for taking the time to answer my question.|||In late 2010 Nvidia introduced their GeForce 500 series, beginning with the GTX 580 and GTX 570. The former has taken over the top spot in the single-GPU speed contest, but it comes at a price that makes two lesser cards in an SLI or Crossfire configuration a more practical option. The GTX 570 is a dialed down version of the 580, but it readily outperforms the previous generation GTX 480. 1.25 GB of GDDR5 memory is standard on the 570 and it has two 6-pin power connectors. It's priced competitively and it's a great card for high-end gaming.|||from nvidia the gtx 590 and from ati the hd 6990 and there are numerous bennchamrks on the web and some says that gtx 590 is faster and some that 6990 is faster, u decide|||go Radeon 6990 most powerful video card to this date