I bought a Corsair Carbide 200R case and it has a i5-3570k not overclocked with stock cooler, and no additional graphics card. There is one SSD and one 1TB WD Black. Stock 120mm fan in front and back, Corsair PSU pulling air from case bottom and pushing it out the back.
The top of the case has two large fan mount areas, currently no fans there. Is there any value in adding a couple 120mm fans up there, running at a very low speed, so provide positive pressure?
Got this from a bit-tec review
While it was good that the front intake was unrestricted by a drive cage, the solid design of the front panel seems to be the major problem, as the front fan can only draw air in through a small area in the sides of the front fascia. Repeating our test with the front panel off dropped CPU and GPU delta T results by 6°C and 9°C respectively, indicating that a lack of cool air reaching the hardware is hindering the case's performance. The empty fan mounts also meant that air was not channelled effectively through the case – we could certainly feel air escaping through the roof of the case before it reached our hardware.
It has an opening with a filter on the bottom for the psu, so if you're pulling air from outside underneath the psu and then out it won't really be adding any heat to the mix.
If it were me I would probably put 1 fanon the side and one in the top. Unless you're not to worried about a little noise you can use low rpm fans - side fan in - top fan out.