I'm not into overclocking, but what is the absolute beefiest and most efficient water cooling and heatsink system money can buy? For both CPU and graphics cards?
The next steps in PC cooling are phase cooling, LN2, and then liquid helium.
Add some good waterblocks and you have a great setup. I would use a single pump and a single PA 120.3 for the CPU and any main component cooling, and the rest in another loop to cool the graphics cards.