home depot has 80-500 cfm inline fans ranging from $15-$35. id get the 250 cfm 8" inductor fan and put that near the top to exhaust the air, and use the 2 computer fans as intakes. make sure the room is somewhat airtight. if it is even though the comp fans are much smaller youll be gettin more air movement then normal due to the exhaust fan forcing them to draw more air in.