This is my 50 cents on the age-old push/pull discussion
Remember: You CANNOT get a fool-proof answer on how to manage airflow. Understanding air currents is a tought science. Even top scientists haven't completely figured out why air currents react the way they do.
Here is how I choose to look at airflow, based on what I've been taught:
Air acts similarly to water, flowing smoothly and causing "whirlpools" if an obstacle is hit. For this analogy to make sense, try looking at your cabinet, when its on its side. Now look at your fans as if they were hoses and pumps, pushing and pulling the water around your system.
Pushing the air creates a straight "duct" of air, untill it gets pulled elsewhere or it hits an obstacle. Pulling the air sucks all the air out from most of your cabinet, except for areas that are obstructed (e.g. the area below a Graphics card). The bad part: You cannot really control where these pulling fans sucks the air in to your system.
If possible, try to find a glass window. Put your case on two blocks of wood, and light a cigaret/scented "smoking" stick. Take the smoke-maker and place it directly below your intake. Now you will see how the intake air gets distributed.
One more thing: Hot air rises up or gets caught in pockets. These pockets affect hardware, effectively heating up other hardware - a viscious circle. Do this now. Put your case on its side again. Now imagine spraying water into your cabinet exactly @ the intake fan(s). Trace the flow: Where are the obstacles. Can you see anywhere where the air gets caught unneccesarily?
Last: Dust only builds up, when it gets time to settle down. So if possible, a bit of turbulence is actually a good thing
- keeping the dust in motion is desired, but alas, not 100% possible.
Eventually, your case will get dusty, and you WILL need to clean it. Creating a positive airflow-case only postpones your cleaning job, and its VERY hard to create such a flow, without sacrificing either fan-grills, dust-covers or - argh, nooo - a silent system.
I myself have now setup a case using only pulling fans. This setup sucks hot air out almost everywhere in my case. One 140mm fan pushes air onto my two GPU's, setup almost like a side-intake (except no hole in side). This one fan also eliminates hotpockets and effectively cools half my MB. In my case, a push fan would just shoot through my case, and out the top 'untouched'.
My last recommendation: Get a semi/pro temperature probing tool. Turn on your system and startup Prime95 AND Furmark. Let this run for about 20 minutes - then pull the case on its side, and start probing the temps Start measuring every possible air hotpockets, and advance around the case. Repeat this procedure at least two more times to aquire consistent knowledge. Lastly: Use this knowledge. Buy a fan to cause turbulence (if possible) when you find hotpockets. Remember that you cannot neglect your HDD's OR ODD. They also get hot. Not so much the ODD, but still.
Thanks for now