Where should I put the additional 120mm fan? Should the fan go at the top of the case, or at the bottom, or should I do both, or maybe two at the bottom and one at the top? This is the case: http://www.newegg.com/Product/Product.aspx?Item=N82E16811233013 Thanks in advance.
So you will have one fan on top, one on bottom, and two on the back? How many intake fans on the front are there? If there are none, I would put one in front blowing over your HDDs and into the case. Edit: looked at the pics on Newegg, looks like there is a fan in the front. If possible, I would add another intake as you have neagtive pressure in your case right now, with 2 intake and 3 exhaust. You could put it on the front somehow, or stick it on your side panel
neg pressure is good, suck all that dust out of your case. i'd put it on the top or the side panel, if you really need to put another fan in there at all.
the way i understand negative pressure \is that that means there is less pressure in your case, which causes air(and dust) to be sucked into your case through random cracks due to the air wanting to be in equilibrium. now if you had a positive pressure, the air would be bursting forth out of your case, through the cracks, and if you have dust filters on the front of your case the is practically no way dust can get in your case.
There's really not enough pressure generated by computer fans to result in either a positive or negative pressure. Just keep your in and out flows balanced and you'll be all set.
