I would suggest that you look at Nvidia which is better supported than ATI,
although AMD is slowly coming around.

How do you know that your card is not supported? If it isn't working properly
that could be for one of many reasons including the wrong driver, or monitor. If
it is from Nvidia or ATI you can build a driver with Envy by downloading the
right one from Nvidia or ATI source code and compiling it for your kernel in one
step. See:
www.maximumpc.com/.../easy_graphics_drivers_get_a_green_light_with_en\
vy

What is your graphics card, BTW? What happens when you click on System |
Administration | Hardware drivers?