Crossfire enabled chipsets are very hard to find, the Intel 965P chipset is one of the few I recall.

I've never had problems with SLI/nVidia, only had problems with ATI so far

Im with DarkLord, i used to have an ATI card and almost all my games would glitch up and/or not load, tried a replacement card, it still didnt work, after deciding that ATI didnt like something o else in my system i switched to Nvidia, worked perfectly 1st time, been using them ever since