But the fans and pump barely take much power? Still don't get it.
If youre willing to live with a 2500rpm fan and a 30degree delta, so your GPU hits 65 degrees or so, you can cool a lot with a 120mm rad.
Don't forget GPUs tend to be designed for higher temps than CPUs. It's not uncommon for a stock GPU to have a temp target of 80 degrees. I'd never let my CPU get that high.