AMD has launched the Radeon HD 6800 series with the HD 6870 and the HD 6850, which unlike what you'd expect, are the next-gen replacements for the HD 5770 and the HD 5750, or the performance-mainstream market. The upcoming HD 6900 series, which is now rumored to arrive sometime before the end of the year, will replace both the HD 5800 and 5900 series, or the high-end performance market.
The HD 6850 has a suggested retail price of $179.99, while the HD 6870 has a suggested price $239.99. Apart from full support for 6-way Eyefmity, AMD claims that HD 6800 series has better tessellation execution that helps give up to 30% performance improvement over NVidia’s competing graphic cards, as well as new features such as morphological anti-aliasing and enhanced anisotropic filtering performance.
How NVIDIA's efforts will compare with AMD's remains a very pertinent question, and for now however, until the HD 6900 series rolls out (the dual-GPU [Antilles] HD 6990 is now rumored to release only in Q1 2011), the GTX 580 definitely holds the crown of the "fastest DXll GPU on the planet", with much more grace than the GTX 480.