your going amd route. so your better of with a ati 6850 cause most boards of amd support xfire not sli. so maybe a amd triple core rana x440 would suit your needs then bump up the gpu to a ati 6870 or 6950. i recommend the 6950
why not use newegg? do live near a microcenter? if thats the case.
mobo for the best bang for the buck is the asrock 870
lowprice. can go x8/x8 xfire.