Generally I go for decent, quiet fans
Tried quiet years ago and did it spectacularly wrong - noise proof case (keeps all the lovely heat in), and two fanless GPUs. It was far more effective to use a case with lots of mesh on it, and expensive quiet fans (the noise profile on the Noctua fans is excellent, but they are fifteen quid each). My main system has at least three fans, plus two GTX480 fans. There's a fair bit of white noise, but it's a comfortable noise.
Compare that to the Powermac, or the SGI O2 box, with one fan apiece, and noisy and horribly noisy respectively due to their fan profiles..
My retro gaming PC only has a PSU fan, and that's inaudible.
Biting the hand that feeds IT
