Corsair CX "Builder Series" are pretty good value for money. The CX500 only has 2 PCI-E power connectors but that will definitely suffice for a single GTX680 and 500W ought to give you plenty of headroom. The two PCI-E power connectors will let you use graphics cards up to 225W without extra adapters.
If you plan on going for a really beefy graphics card, like something that is heavily overclocked, see if you can find a deal on the Antec 620w high current gamer PSU, which is balanced towards more PCI-E power connectors, and all are 6+2 pin.
Both of these are 80+ bronze rated, so whilst not the most efficient PSUs you can buy they will at least be reasonable performers and shouldn't get too hot or noisy.
Some people ask me why I have always enclosed my signature in spoiler tags; There is a good reason for that, but I can't elaborate without giving away the plot twist.