Well, Micro-ATX boards tend to not be great for overclocking (though I don't do that), and many only support 2 sticks of ram (I have seen some that allow 4 though). Quite a few of those cases don't allow bigger gpus and cpu coolers - in this case, the evga 550ti's PCIe 6-pin power connector just barely fits, bumping into the hard drive cage. It wouldn't work if it were smaller.