Ya know, Im not sure about case temp, really. Heard it somewhere here, but I cant remember.
It should matter which way the air is flowing, but it should flow in one direction.
Im not sure how well sucking the air from the bottom would work, but if you put one in, just make sure it will suck air in.
Personally, and because this is the only way other than a case mod, I have the airflow going from front to back.
Heres my set up:
Since the ATX PS connecter to the mobo prevents me from using the lowest 5 1/2 drive bay, I put a HDD cooler in to suck in air. On my processor now I have this Kiwi orb cooler. Mounted on one side (its down when the case is standing) is the fan off my coolermaster, and that works quite nicely cooling my cpu off. Since there is a spot for a case fan in back, I put one there to suck air out. Since my mobo, Asus A7V, cant use the PCI 2 slot, Ive used a slot fan with adjustable length for it.
My temps for cpu and mobo at highest Ive seen
CPU: 41C/105F
Mobo:27C/79F
I dont know how well your setup will work since the Power supply may interfere with the airflow, but keeping it in one direction is a good start.
Wish I could remember about the case temp. Mine really doesnt feel warm at all...