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.
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