Having shamelessly stolen Danny's excellent research I've finally finished building my new quiet server for MythTV, Squeezecenter and other serverly duties. It's brilliant!
The Antec Mini P180 case and Antec NeoHE power supply provide the core noise reduction. The case is solid and with an enormous, but slow, fan at the top of the case providing quiet cooling. The mounts for all the drives have little silicone grommets to cushion their vibrations. Seems to work very well with my four 7200 RPM SATA drives, which previously resonated inside the case and made a very loud, high-pitched hum that was audible from the lounge room.
I don't yet have the CPU heatsink, as my supplier sent the Xeon version instead of the 775 socket version. The supplied Intel fan is bloody quiet anyway, only moving at 800 RPM. I'm sending the heatsink back and will see if they'll give me a refund instead of a replacement.
The result is that unless you put your head almost inside the cupboard, you can't hear the computer. This contrasts rather well with the previous systems, which had quite the roar going on. Cooling is okay, though I'm gonna have to keep an eye on it. Running two burnP6 processes sees the temperature (presumably CPU, but lm-sensors labels it core 0 when another is CPU temp) shoot up to 61 °. Perhaps that big mama heatsink will help there, as it's not the ambient temperature in the case that's the problem. See the graphs.
In fact it's so quiet I'm tempted to move it into the lounge room so that we can use the MythTV software for playback, rather than the PS3 which has plenty of problems with file formats (though has spectacularly good picture quality). If I can convince the boss of the merits, I might buy one of the more-appropriate HTPC cases and move all this hardware into it. Then I'll build myself a nice quiet desktop. I'm sure she'll claim this was my cunning plan all along...
I'm very happy with this system. Total cost around $650. Thanks for letting me steal your research Danny!