A little bit expensive. I think it would be cheaper to build a "normal" PC and an outhouse for it, along with all necessary KVM switches, if someone really wished to go that far for low noise.

I went the low noise route recently with an Antec Sonata. It has a pair of 120mm fans that move a lot of air throuh the case with almost no noise. A giant copper heatsink with a 92mm fan is on the CPU (similar in idea to the 120's - lots of air with low fan speed). The Sonata came with a nice power supply as well. I topped it off with a few things such as rubber grommets everywhere to keep the fans, hard drives, etc. from actually touching any metal (and perhaps transmitting vibrations), and a 5-1/4" 4 channel fan speed controller with an LED display for speeds and temps. Also have a fanless "giant damned heatsink" for the video card to put on next.

All-in-all it's very quiet already, and the system runs even cooler than before with all the rest of the fans I once had. I'd recommend it to anyone - to me, getting rid of the noise was more important than looks. But my PC sits under the desk so...