What's the deal with Water Cooling anyway?
Why wc setup, pump+fans can be near silent, yet classic GPU cooling can't?
You need to have a certain amount of air pass over a certain area of heat sink to be able to adequately dissipate a certain amount of heat. You can only make a heat sink so large and still be able to strap it to the chip, therefor, once you reach a size of heatsink where it is impractical to make it any larger and add more fans, the only thing that you can do is make those fans spin faster. Look at the length of some of the triple fan GPUs, they can be over 10" long and still use only 92 mm fans instead of 120 mm fans. Look at the size of the Noctua D14, it can block the 1st PCI-E slot on some motherboards so it is impractical to make it bigger. The weight of these coolers hanging off of the PCB is also a problem. Additionally, on GPUs, the PCB itself restricts the airflow behind the heatsink.
Water coolers are able to use thicker, wider, and heavier radiators with larger fans. By decoupling the radiator from the PCB, some of the weight and space issuers are resolved. As a result of using more fans and larger fans to blow across a higher surface area radiator, each fan can spin slower to achieve the same cooling performance. Fan noise tends to be non-linear with RPM, that means that two fans spinning at 800 RPM make much less noise that one fan at 1600 RPM. The water cooling trade-off is that the pump also makes noise, there is additional cost and the system is more complex which makes it more prone to failure.
Imagine strapping the radiators and fans from an EK X240 to your GPU. Because of the thickness of the radiator and the full sized fan, it would block 5-6 PCI-E slots (ALL of the slots on 90% of boards) and it would probably rip the PCI-E socket off of your motherboard.