|That is all that is need is a small hole in the front. The means of getting air in at the front is probably a lot bigger than you realize as any old gap will do and cases are not made airtight. The quicker the rear fan can exhaust the air, the quicker the air will enter at the front, otherwise you would end up with a partial vacuum in the case and you would need a huge fan to do that.|
A smaller hole can be beneficial as it will set up a venturi effect. (google it) This has the effect of cooling the air as it enters the case, a very desirable effect.
Bear in mind that as the air in the case heats up. Hot air expands and rises so it will find its way to the top of the case naturally. You need a bigger exhaust hole because you are exhausting a greater volume of air than is coming in the front.
I would forget about fans on the side of the case, certainly not one taking air in and the other taking air out. That will just disrupt the air flow within the case and possible cause hot spots of stagnant air.
message edited by StuartS