Well, the Vantec fan is 84CFM.
But really, I used one of these for a while with an 80mm Enermax adjustable speed fan at the lowest setting (on an AthlonXP 1700+ @ 1900+) with absolutely no problems. I never tried more because I'm not a voltage jacking freak. With the Enermax fan, the thing is almost silent and cools well.
I've never used the Vantec fan I'm including other than making sure it works. It is really too freaking loud to be practical for me but if you're an overclocking feind you won't find more CFM in an 80mm fan, I think.
I bet the combo really cools like one bad mofo...
C