There are two devices in this class, NVIDIA GeForce 6800 GT and ATI RADEON X800 PRO, both priced at $399 by their manufacturers.
The NVIDIA GeForce 6800 GT looks overall more appealing than ATI RADEON X800 PRO due to its 16 pixel pipelines. It does slow down in games that require high pixel shader performance, though. Half-Life 2 is the most conspicuous example.
High resolutions and situations when a high fill rate is important are the conditions under which the GeForce 6800 GT can show its best. The RADEON X800 PRO, however, often beats it across a number of games in the FSAA+AF mode.
The reason for that is typical: the RADEON has highly efficient anti-aliasing and anisotropic filtering algorithms, an efficient memory controller and HyperZ HD technology which helps to make the best use of the available memory bandwidth.
The ATI RADEON X800 PRO is smaller and quieter, yet we would still call the NVIDIA GeForce 6800 GT the best choice for about $400. Some samples of the GeForce 6800 GT can overclock to the frequencies of the GeForce 6800 Ultra, while the RADEON X800 PRO, however well overclocked, still has 12 pixel pipelines against 16 of its competitor. Theoretically, it may be possible to unblock the four disabled pipelines, but some of them may be really defective and the card wouldn’t work correctly then.