I've recently updated my computer from an Athalon X2 3800+ Socket 939 to an Intel Q6600. With it, I changed my case from a CoolerMaster Centurion 5 to an NZXT Zero. This has given me major boosts in cooling, with what I'm dubbing the "ultimate fan cooling case." The old case had a rear mounted 120mm fan and a forward 90mm; the front of the case was also bezeled, meaning that there were a bunch of holes drilled in it like a screen to allow "neutral" airflow (ie, no fans provided airflow). My new case has eight 120mm fans--two front, two rear, four side, and a top mounted 80mm fan. The 80mm is not connected because my power supply is about three milimeters two big; I squished the fan in place, but it makes an annoying noise. Using my motherboard's utilities, I've noticed that the CPU averages at 30 degrees C and the system at 35 degrees C. Now, that may not seem like much, but because of the power optimization features included in much of the new hardware, the majority of my fans aren't running since they're not needed. On top of that, there have been a few occasions where the CPU cooling fan has shut off because the processor is cool enough (it came with three installed heat pads, plus I added Arctic Cooling thermal paste). The stock heatsink probably has at least 1.5 times the surface area as my old one with the X2, allowing for greater cooling*. (*The reasoning for this is a law of thermal dynamics that roughly states that heat moves from high concentrations to low concentrations.)
While this does cause me some anxiety, I am confident that my computer can handle any temperatures and can easily cool the entire system without breaking a sweat. Though I have no immediate plans, in the future I may possibly overclock this rig, and I feel that I could do so using everything that is factory-stock, both for the CPU and the case. Add to this the fact that fan is silent; I only hear noise coming from my case when a fan revvs up or when the ROM drive does the same.
I highly recommend this case if you are in the market for a new one or if you are worried about your computer being cool enough.