It depends on what clock speed you wish to achieve with the CPU. The Asus Maximus VI Hero motherboard is designed for high overclocks so if you are going that route, a high end closed loop liquid cooler or custom liquid cooler is probably the best fit. But there is a Maximus series board that comes with a water block on the VRM which is designed for more extreme OCs and would go nicely with a custom liquid cooler. To get to these high clocks (5 GHz +) it might be necessary to de-lid the CPU heat spreader and apply a better thermal paste (which will void the CPU warranty). If you just want a modest OC like 4.5 GHz, an air cooler will be enough.
Which closed loop water cooler do you recomend for at least 4.8 ghz?
4.8 on an AIO cooler is going to be difficult. 4.5-4.6 is doable with either Corsair H100 or noctua type air, but 4.8 without a custom loop, especially with the sli 760's in the case is going to be very difficult if not impossible.
If you really want to push 4.8 and up, check over on the water coolling forum at overclock.net for ideas.
4.8 will be rather iffy, Asus did some testing and found out of a couple hundred 4770Ks they were only able to get 10% up to 4.8, so if luccky enough to get one that will do 4.8, will prob need to look into a custom loop, I run 4.6 with a CM GTS V8 and can run 4.7 (but not for 24/7, for me anyway), the V8 runs a couple degrees warmer than an H90 and about 12 degrees cooler than a 212, about 8 degrees cooler than the Phantek, with high performance fans it's suppose to run even cooler (haven't tried it yet), can see results from Asus on the Silicon Lottery here: