The ATI R600 will support DirectX 10 and may be the fastest DirectX 9 card too:
R600 will be designed to run DirectX 9 code just as fast as it is supposed to run Direct X 10 code. Unified Shaders apparently can run code that gives a toss about Pixel Shader and Vertex Shader just as fast. There will be an abstraction layer that will decide whether the information is pixel, vertex or geometry, and it will be served by an adequate hardware pipe. So we don’t think that the DirectX 10 hardware should care that much about the DirectX 10 versus DirectX 10 code.