No, it means you can run either crossfire or sli, not both. That is impossible by software and hardware terms.
If you are building for the first time, dont buy something so expensive. $400 dollars for a motherboard is insane.
Also, i dont see why you would want to run amd cards with nvidia cards, get multiple amd or multiple nvidia, no point to mix them up at all. There is no point in getting the best of both worlds, because both worlds are pretty much the same except that nVidia has physX