An important thing to consider with airflow is if you are drawing from an area that is hot, you are going to be blowing hot air onto your already hot CPU. Power supplies by their nature run hot, especially when they are smaller and working harder (just pick up your laptop power supply after an hour of rendering). Because of this you’ll be blowing hot air onto the CPU which has an effect more like a hair dryer.
Ideally you want the flow to be reversed - use the fans to extract the hot air from the case which pulls the heat away and will draw air through wherever your intakes are designed. In most cases, the front of the PC case is the intake because the only thing up there are drives which do not get nearly as hot or take up as much space. In cases like the Mac Pro, the vents are on the bottom so that the cool air can be drawn up and out the top since heat rises.
What you might be able to consider is using something like a closed loop liquid cooler (google Corsair H50) that was integrated into your case. If you considered the radiator as part of the design, you could design around it to make it more integrated.