Avoid the hassles, go and buy an nVidia card, they have far better support in LMCE. You do not need a high end card. 6200-7300 chipsets are just fine... 8xxx series cards will ultimately provide hardware acceleration, but again, not necessary at this point.
Read the Display Drivers wiki on how to install the latest nVidia drivers, once the card is installed. The only other thing to think about is disabling in BIOS your onboard chipset if this is possible. If it is not, you can work around it quite easily at the command line.... come back then if you have this issue, and we can provide instructions for that.