You are looking at it wrong. The reason to use water cooling is because it's simply a superior
performance solution to any reference blower in the world - lower noise levels and temperatures and overclocking with reduced penalty for increased level of noise and temperature that otherwise occurs under air.
295X2 runs
10-20C cooler + quieter than a Titan X while using ~450-500W of power because of a single AIO CLC. Titan X at stock speeds operates at 80C+.
I think a lot of people don't understand just how much superior AIO CLC is to air. If you overclocked Hawaii to the max like that on a Titan X's blower, your temperatures would probably be 90C and crazy loud.
Max overclocked Hawaii uses a lot of power.
Despite that, a single 120mm AIO CLC keeps the card at 80C max.
That means a theoretical 300W 390X would run cooler and quieter than a 250W Titan X and easily cope with 350-400W overclocking. With Titan X's overclocking, noise levels skyrocket to uncomfortable levels. Just because the Titan X's reference blower is better than 290X's, doesn't mean it's a great solution at all. In fact, it isn't -- it's loud & can't maintain high boost for extended periods of time in overclocked states. That's not a knock against Titan X itself, but simply a fact that blowers by design are inferior in performance, noise levels and overclocking to the best after-market open air solutions or AIO CLCs.