That is one hell of a beast
For 2 overclocked 680s you will want at least 800W Power supply, something like this
http://www.guru3d.com/article/cooler-master-silent-pro-hybrid-850-watt-psu-review/5
But the powersupply is something that you shouldn't skimp on especially on a super high end build like that. And it may be worth getting a 1000W high quality PSU just for the extra efficiency under high load.
As for CPU cooling, there a pros and cons for both air and water. Water coolers are generally more efficient but they can be harder to install and cost more. Unless you plan on doing some heavy overclocking there is no real need to go for a water system, SLIed 680s will already be very load so the noise from a decent CPU cooler won't really be an issue.
If you want a liquid cooling system and want serious overclocking then there is the H100 http://www.guru3d.com/article/corsair-h100-review/1, but personally it looks like too much of a pain, I mean that radiator is huge. Intel make a good water cooler BXRTS2011LC which is a bit more reasonable.
The Cooler Master TPC 812 seems like a more reasonable priced alternative which uses a vapour chamber design. And supports overclocks up to 4.6GHz on the 3930k which should be more than enough for anyone.
As always make sure that you read plenty of reviews and get other opinions tho. I can't say I have any experience with such high end gear myself.
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