Well, imo, the best air cooling you can get is the Vantec tornado w/SLK-900U, it probably won't beat the best water cooling setup but it's certainly a lot easier to set up, and certainly a lot cheaper. Sure, the noise will be an issue, but you could always get some fan-controlling device and you'll be good to go.

Personnaly, I'd be scared to use water in my system :p
I know there's no real risk when you're careful. Maybe I'm like that because I only have one pc and no money: if it goes down, I'm left with nothing.

To me, the only reason why you should go to water-cooling is noise. Because you can get extreme cooling from air. Or go with a less efficient fan and put a couple of case fans. I'm sure your hardware will be maxed out before the temps go to high. I'm not really experienced in oc but that's my opinion.

Or put 4 Vantec Tornados as case fans