Hi you could put 2nd fan on rear of cooler but top fans id always have as drawing air out and cases run cooler with neg pressure to positive pressure ie pulling more air out versus positive which is pushing more air in as you get less "hot" spots with air pockets like if you have one rear exhaust fan and space above like with top psu or where it could be if can have top/bottom mount so the air above rear exhaust is holding warm air which isn't what you want.
Why don't you run fans from molex's and just one from cpu header so keeps that quiet! as the more headers you use from mobo the more heat and volts drawn!(if i connected delta to mobo it would prob fizzle then pop as tracks and vrm's blow 3.4+ amp load!)
Only have cpu fan connected rest runs from one molex cable for delta and top rear fan and 2nd molex does front fans and dvd drive HD drives run from there own sata power cable.
One other thing is air speed/force as opposed to air to and frow as if you can direct air with enough force/control you get chill factor.
As you said air's a weird thing to deal with what with thermal currents/eddies and more take for example something that's at an angle or flat across flow one side will be warmer than other as pressure will be lower on rear side of it.
You could even do with two different fans?front one high pressure rear one high flow but wouldnt need to be high static though or something like that as front would form air up then 2nd would shift it.
As could get something like what you get with aeroplanes and boats with jet wash with front one moving air around then 2nd isn't able to compress and shift air fully or could even be bouncing off it so reflected?
Can just imagine you now! tick tick x=y-Q~Xa% of 9. then playing with smoke markers?.lol mind you the smoke makers what they use for flume testing would be a good idea to see flows etc esp if you could get some clear plastic to cover sides so can see plus have lighting inside to illuminate it.
Lian li do a compartmented case (V1000's+ server case's) which have mobo butt upwards along with gpu! rear fan is configged/designed to be an inlet then exhausts out top through mess and psu/hd's are below with a panel between them and mobo area not sure how effective it works though?
Mind theres some cheap case's out there(Bigger!) as newer types are wider(more depth) for high coolers.
There was a new Aerocool Xpredator case went for £50 on flea bay other day. quite liked that myself.
One's to avoid are the ones with too much plastic as not a great cooler.(We need them made out of silver or copper?)best conductive elements then could get nearer passive cooling?
Delta along with san-ace/Sanyo Nidec which make Scythe GT's./Papst etc make some good fans which many use for servers.
Delta's have 6 coils in motor where as most fart/retail fans have only 4 so not as smooth or powerfull ie torque which gives you better static as keeps speed while pushing air through rad's etc.
You can find plenty on flea bay as used server ones or new(if you need part numbers or lists etc ive some sellars saved plus find right types.
There are some up that Delta make in 25mm 120 3 bladed that have great static pressures.
Not all there fans are PWM many are 3 wired.
But Delta's and sanace etc are really controllable as can run @ really low volts unlike many retail fans which stall or burn motors or very unstable when slowed down.PWM is the future really as not wasting power turning into heat with a controller(rheostat).
.Edited by oscarbravo - 5/10/13 at 6:59am