Case type 2:
We personally like the above setup best. It has one 120 mm fan as intake and another one as exhaust. We like this set up since it has only two fans so lesser noise and since they are 120 mm they move more air. Though cases with such an arrangement, especially the front 120mm slot are slightly on the expensive side. Antec SuperLanBoy is one case with a similar set up.
Case Type 3:
The above arrangement is the bare minimum we would recommend. Most entry level cases come with two 80mm slots. Make sure you mount the fans and orient them to intake and exhaust.
Many of our users complain that the inside of their case gets very dusty. Of course you cannot eliminate dust altogether but by following these simple laws of physics you can tweak your setup.
Good try.
