Well I have been experimenting with my case, as I have a 92mm front intake, and 80mm rear exaust and a 120mm top blowhole.
Now right off the bat you can tell that I am exausting more air than I am blowing in, so I am currently setup the front and rear fans to blow in with only the top blowhole as the exaust. But I have not really seen any differnece in my temps, but have noticed that my case is a little less dusty with the positive air pressure inside the case as opposed to negitive pressure.
So I really think it is a matter of case design, air volume, and air pressure. And as we all know that varies greatly between cases.
But I agree with ming, that that setup should be the starting point at least. But don't be afraid to experiment.