Kind of where my dual 680's are at, hitting max OC on air and even using an external high CFM fan to get air to the second card didn't help that much. At this point I am about to go water. I would love to see a couple pictures of your water setup, what size fans and radiator do you use? What type of circulation pump are you using and is it a closed or open system?
For me, I would have to do some heavy modifications to this case, Silverstone Fortress FT02, but would be able to fit a radiator that is 3X180mm. I designed a couple layouts and decided that an external radiator like the Resonator with radiant cooling fins and a fairly high water volume would allow a higher flow pump to run three simultaneous lines to each of the GPU and one to the CPU, doubt I would bother with any of the onboard chipsets with 3X1800mm fans blowing directly below and over them.
A couple years ago I got the idea to take one of those smaller compressor and heat exchanger based mini fridges and turn it into the heat exchanger for the computer. Basically, take a very long run of stainless steel tubing, id to fit what ever fitting you plan to use, and create a simple expanding coil out of that stainless steel tubing inside the fridge. Just braze a fitting on and you now have a pretty massive watt muncher. Trouble with this setup is either spending the time to get the temperature of the fridge just right above the dew point for your setup. Forget the measure but anytime two adjacent materials have a heat variance of so many degrees you hit dew point and get condensation. Condensation is bad but some have used non-electrolytic grease to pack in around the CPU to protect it, not seen any long term reports on the success for one of these systems. One of those tasks to be attempted down the road, on a system running outside a box on a bench setup.