I bought an ultra-quiet power supply from PC Power and Cooling and it was, in fact, totally silent. It's fan is so quiet that sitting in my office I could not hear it running. I could hear the hard disk, but when it spun down (power savings) the box sounded like it was off.

They make very quiet CPU fans as well.

A while ago, I saw some solid state disks packaged just like the regular spinning kind, but built with NVRAM or something like that. Very fast. Very expensive. Very quiet. Now that I think about it, probably very hot as well....

There was a company called Ergo that used to make a system called 'the brick'. It was very small (for those days) and had no fan. The case was one big heatsink and they used a clever device to transfer the heat to the case. It looked like an anti static bag (size of one wall of the enclosure, about 3 mm thick) filled with some sort of heat conducting liquid.

You can replace many 'fan required' situations with an oversized heatsink that has outside the case exposure, as long as it has good contact with the hot component. (don't forget the heat sink compound).

Hmmmm maybe that would be a good oddball case direction, something that looks a bit like a porcupine, lots of external heatsink on the case itself....