BonzaiDuck
Lifer
On item 2, I'm not sure what you mean. We build up pressure inside the case with the intake fans. The CPU-Fan pulls this pressurized air into the duct box, and the exhaust fan pulls it out of the duct-box and out of the case. This latter fan will also pull additional pressurized air through the seams of the duct -- hence it is a good ideal to cut the duct so that it fits closely to the motherboard. You can even use components -- like the VGA card or RAM modules as "part of" the duct paneling, with the idea that narrow apertures between the duct-panels and these components will allow additional air to be drawn past those components.
Using the Ultra-120-Extreme, I've devised an improvement in ducting over my Prescott system for my Core-2-Duo build. The 120-Extreme doesn't much allow you to push air down on the motherboard, so I have a 140mm intake fan sitting behind a ducted hot-swap drive box pulling air from the front of the case, and additional ducting directs this air directly at the broad face of the CPU cooler. A 120mm exhaust fan assists in pulling this air immediately from the case. Another 120mm exhaust fan is ducted to a flat Lexan panel that sits below the 120-Extreme duct-tubes, and very close to the motherboard, so that it draws more pressurized air from the case, past the motherboard components, and out the fan exhaust and out of the case.
Any surplus pressurized air that doesn't leak into the duct box for expulsion is going to force its way through the PSU fan and vents. Everything else in the case is sealed off. Ultimately, as enough pressure builds up inside the cool part of the case volume, the intake fans become less effective, but all of this case air is going to go out of the exhaust through three paths: past the CPU cooler, past the motherboard components, and through the PSU.
On the issue of top-side fans -- true -- heat rises. But there won't be any hot air escaping into the unducted case volume area. So while I tried top-side blowholes in earlier builds before I began working with ducts, I don't do it anymore. The objective is to reduce the number of fans necessary, and make them more effective by isolating heat-radiating components within the path to immediate exhaust from the case.
This raises the issue of noise mitigation. Ideally, it is better to have fans sitting behind the hard disks and in the center of the case of their intake comes from the case-front with no leakage of air already in the case to the fan's intake side. It is also better to have fans in the bottom of the case drawing air off the floor, but the case must be suspended (on wheels, for instance) to provide airflow.
This is why I prefer full-tower cases, because there is a better chance of deploying fans like this, and it makes building and installing the ducts a bit easier. But otherwise, without these features, one might prefer a midtower case for the same reason people cite as a problem with (unducted) pressurization of cases.
