XFree86 3.1.2 currently doesn't support the advanced features of the 9400. The timing for the release of the 9400 was just bad for the release dates of 3.1.1, so they weren't able to add the support in. Now that the card is pretty popular and a new release is expected soon of XFree86, we expect to see direct support in the next version of XFree86. For now, you can run resolutions all the way to 1024x768 at 60 hz. If you have trouble using Xconfigurator to set it up, you will probably find that xf86config will do the job (it just doesn't look as nice doing it :-)