Automobile manufactures have always blown air INTO the radiator from air that is outside of the vehicle.
So following this concept would prove very logical to blow the coldest air through the radiator, either blowing in either direction but not in a suction manner.
In other words, make sure to blow into the radiator/water cooler as opposed to trying to suck air through from any side. Your results will be greatest if you are blowing air through the radiator, and exiting the hot air OUTSIDE of the case somehow.
Remember these rule of thumbs:
1) Blow, don't suck through the radiator.
2) Ensure that the air going through the radiator (which is usually warm to hot), is exhausted outside of the case, rather than blown back in.
When you're hot, do you stand in front of the fan, or behind it?
Basically, the physics of it is, when you blow air onto a surface, it slightly compresses and becomes denser, allowing it to take more heat away with it. Where as behind the fan, the air getting sucked in is stetched and becomes less dense = less heat carrying capacity.
Not a dumb question at all, but one which can be figured out fairly easily.
There are no stupid questions, only stupid answers. :wink:
As for the fan setup, I have found that it really depends on the fan and/or radiator. Hook it up both ways and see which one produces the best result.
You could also put a fan on each side of a radiator, volt mod a plug (+12vdc and +5vdc) and run the fan(s) at 7vdc for less noise.