Depends on the temperature of the air coming through the casing. Visualize the air flowing through the casing (based on the location of the ventilation holes) and decide which sets of ventilation holes are more likely to have the coolest air flowing into them (based on your installaton). Then design your ventilation system to take advantage of that.


Hugo suggested a top fan blowing out IIRC, but it might be worth considering it blowing the other way (i.e. inwards) - especially if you're not a weekly car cleaner. It is relatively simple to put a dust trap over the fan, and the resulting positive air pressure in the empeg will keep dust from entering through any other vent. Having the fan suck air out will result in a negative case air pressure, and dust would be sucked into any other 'vent' in the case.

Probably not a big issue, but something to consider. BTW, this applies to your PCs as well - most PCs have negative case pressures due to the extraction fan in the PSU. Take the lid off of a PC after 6 months, and you will find a lot of dust in there, helping to cause premature fan bearing failure to your athlons HSF. Installing a filtered case fan blowing inwards can cure this.