I'm not sure if that's necessarily true, Mike. My Zalman heatsink/120mm fan blows air directly onto the CPU, as do most heatsink fans. By blowing air directly down on the CPU, it blows out and away creating a flower effect... it pushes air down onto the heatsink, increasing air flow through and away from the CPU. So my suggestion, as long as the fan is fairly small and can be directly fairly accurately, is to blow air directly on the CPU. Again, that's not a great way to do it, but it should be effective. I would say that moving air in any direction in the case would give you at least SOME of the desired effect, especially if you're opening it up to do so.
Sidenote: I'd rather have an exhaust fan than an intake fan.