Don't know your budget, but I would reccommend going for a 580 or 590 instead of what you choose, another thing i would consider, is buying a prebuild one , a DELL/HP since these computers are thought out by engineers who studied the subject a lot longer than you and I .
I myself have a HP XW 6600 workstation and it works just fine never any hick ups for about 2/3 years now