I think it's great this guide has helped many with their air cooling. However, my take on silent, high-performance air cooling is different. Here's what I've learned about it. I'm sure these points are not new or exhaustive. Please use or disregard as you deem best.
- Insulate the case with sound deadening material in an attempt to make it air and sound tight.
- Use only one intake fan with a fan controller, 92mm or 120mm, 30 to 40 CFM. Position it no higher than the HS so a duct may be positioned from it to the HSF. Depending on the case, the intake fan can be positioned in the front, bottom, rear or side.
- Put something about 6" from the outside of the intake fan like a piece of carpet to absorb sound.
- Duct the intake fan to the HSF.
- Use an 80mm HSF (optionally ducted to the HS) or a 92mm HSF ducted to the HS, 30 to 40 CFM
- Position quiet 80mm fans inside the case to blow directly onto components needing air cooling, 20 CFM max each. 7 Volt mod or use fan controllers if necessary to quiet each fan.
- Use a quiet PSU that is powerful enough.
- Use a passive exhaust near the PSU exhaust to augment the PSU exhaust and help neutralize the positive air pressure.
- Don't bother positioning additional fans to direct air flow. Just let the hot air exhaust on its own.