To make it short - XFree86 is a piece of software that displays everything in graphical mode. It handles screen, resolution, mouse, keyboard, places windows etc. It doesn't draw menus - it's window manager part (KDE, GNOME, Enlightenment, Window Maker, Fluxbox etc).
If your graphic performance is not good, it's because XFree86 driver for your card, I guess. You may try this driver: http://www.ati.com/support/products/...uxdrivers.html