Looking at this setup it makes me want to water cool my whole computer.
Could you do us a favour and maybe point towards a place that explains watercooling well? German is ok for me, others might prefer english.
What I don't want to see is basically me checking everything, realizing that there is still something I need and then realize I have to wait three days for it to arrive... that would be unprofitable

i would stick to this
http://lifehacker.com/5940236/a-beginners-guide-to-water-cooling-your-computerLooking good. Now I would love to understand how to calculate how much dissipation one of these rads can handle, could anyone help me?
I have six boards. From the conservative side I calcualte that a board at max speed takes up 70 watts very conservative.
So, 6 times 70 is 420 watts in power usage, I am not sure if this is correct, but I will simply use a "nothing lost" calc and assume that I need to dissipate 420w in heat.
How do I now calculate, how much dissipation the radiator brings? From what I see, with six boards I am assuming that a dual 120mm XSPC variation would be fine. And I would love that. I would use their kit with pump, buy more adapters, filling rings and buy more hoses and am done with it.
Did I understand that right? Damn, im a watercooling newb...