During a fresh installation of RH7, the graphics card - a Matrox G200 8Mb SDRAM - was correctly detected. Unfortunately, when I started the XServer, it was extremely slow - I could literally see the pixels of icons being drawn. The system is an Intel Celeron 333, 192Mb RAM with 8G hard disk. The card functions correctly under 6.2 (this is still on the machine in another partition). I eventually got things running normally by asking X to generate a config file by itself.
Are you using XFree86 3.3.6 or 4.0? Does running Xconfigurator fix the problem? Xconfigurator --preferxf4? Xconfigurator --preferxf3?
Using XFree 4.0 I fixed the problem by running "X -configure" and using the resulting config file.
Looks like you got it going ok..