As long as the card priced around 330-360 its a good buy I got a 7970 direct cuII top which is equilavent to a 7970 Ghz edition @ $360 recently , sold it off at $400. I guess lightning would sell around $400 other non reference cards probably around 330-340 with warranty. I've seen no warranty ones go for $250 if your willing I take the risk. One thing id advise against the 580 cos it's a power hungry card compared to the 680 and the perfomance vs price your better off getting a 7970 or 680. Which is only $50-100 more. Only thing I would advise in your choice of either 7970 or 680 , is the biggest benefit for now of the 7970 is mantle if you play games that support it and stock settings it perfoms about 5-10 frames better & a ghz edition just wins a reference 680. While the 680 is better if you want more stable drivers(argue-able) and shadowplay , which is the best video recording software to date with minimal fps losses. But saying this amd is due to release radeonpro which is amds version of shadowplay , not confirmed but it's on it's way. So when it comes to these 2 cards leave it up to your preference! But one thing to note if you decide to put the 770 into the picture this is nvidia's 680 ghz edition it performs better or same to a 7970 ghz.
Source : had both cards 7970 top and a palit gtx 680 with waterblock stock settings. Saw a minor jump in fps after getting the 7970 top.
