what are your current temps? I have mine under water... that is way more than enough for that chip. I would go with a laing pump personally.
I really don't think you're going to make it on the basis of watercooling. Your mobo may be holding you back, and when these chips hit their ceiling, they hit it HARD. Like going from 4.071 GHz to 4.15Ghz isn't stable even if i add .18 volts. Maybe that's just my C0 though.
Also these suckers can't take much more than 1.45V for 24/7 usage, and even thats really high. Electrical leakage will get you before temps.