nVidias new 6800 is only being released as a 400MHz card in the AGP platform at this time. The 600MHz that you are referring to is the clock speed that the chip is capable of performing in an environment suited for that kind of speed and amount of data at one time. That new platform is the new PCI standard, called PCI Express.
nVidia does have very good hardware, the main problem with nVidia is their drivers. It is amazing what happens when they finally got a new driver. It just happens to be programmed by the same company that writes the drivers for ATI. Drivers are the driving force for the hardware. See the article from TomsHardware for benchmarks on the new drivers, as well as, the new explanation of PCI Express. http://www.tomshardware.com/graphic/20040414/index.html
If you are going to wait for October, then you might as well wait for the new PCI version and get a new motherboard at the same time.
This is the main reason I haven’t bought a new 800FSB mobo this past year. I am just using my 533FSB until the new standard comes out.
The first mobo and video cards with the new PCI should become available in August and become openly available in late September to mid October. But you never know what’s going on with dates these days. Because wasn’t there suppose to be two new games last Thanksgiving called Half-Life 2 and Doom III?