Hey, honestly, waste of cash. Watercooling is only needed for extreme circumstances or if you have cash to blow. GPUs are a-ok up to ~100C. My two 5850s are overclocked and don't go over 70-73C. Meanwhile my CPU (i5 750) is overclocked from 2.66ghz to 3.75ghz and I have air cooling for it as well, temps are totally fine. I can do 4.13ghz on air with this.
So yeah, it's far more cost effective to invest in a good CPU air cooler, and for the GPUs, the twin frozr that Hawk comes with one of the best and quietest available. Try it on air before making the jump to water cooling. I've priced a cooling system for my GPUs and CPU, and it would be ~$600-700 for anything decent. Meanwhile I spent $65 on my CPU air cooler and I upgraded from my reference GPU coolers to super quiet Scythe Setsugens for $40-50 each. That wasn't needed but they're way quieter. Besides that, a case with good airflow is quite important. Extra case fans are only $10-15 each.