I don't know if it'll be quieter, but it'll be cooler alright. Swapping an air cooler for a water cooler is good if you want to get higher performance; however, I think that it might be considerably quieter since it'll probably be 200% cooler. The only problem might be the fact that you can't really control the fan and pump speed automatically, so they'll constantly run at the temps you predefined and not according to those of the GPU.