You will want to download the latest version, 4.2.0. It has more support for your higher end graphics boards these days. Check out xfree86.org for more information on supported hardware. A decent ftp site to get it : ftp.rge.com - it's pretty easy to navigate.

you will probably first want to download and run Xinstall.sh ("sh Xinstall.sh -check") for verification of the files required for your distro. Once you have all the files downloaded, from the directory you downloaded them to, run "sh install.sh" and you will be walked through the installation process.

Once the install completes, you will want to create a basic XF86Config to give the new X a spin. Easiest method to incorporate support for video board is to run "XFree86 -configure"
This will create the file /root/XF86Config.new - copy, or move the file to proper location (ie "mv /root/XF86Config.new /usr/X11R6/lib/X11/XF86Config")

Once you have done that, ensure your .xinitrc file exists (ie /root/.xinitrc) and that it points to your favorite window manager. Should only require one line for this to happen. (ie. for gnome you would typically use "gnome-session")

Hope this helps.
Regards and good luck.