I just received the Shuttle PC62 power supply.
For those not familiar with it, it uses the 200W external power brick similar to the famous (infamous?) Dell Y2515. In conjunction with a passive DC/DC converter to produce 5 and 3.3v rails, it creates a totally passive power system for most G series Shuttles.
The limitation is 200W, but with prudent selection of components, 200W isn't really much of a limitation.
In my Shuttle, I've replaced the fan with a Nexus 80mm mounted using the soft rubber mounts, and with this power supply, the only noise from the unit is the hard drive. I tested briefly with a 2.5" solid state drive, and the unit was completely silent. I have not put a CD in the optical drive, so I don't know how much noise that would be, but that's to be expected.
I'll be testing this power supply with a Dell XPS 200/210 shortly, as well as seeing if I can use it in my full ATX setup as well. Since it's Shuttle's odd form factor G power supply, fitting it in other cases could be challenging. Also the cables are fairly short, as they are intended/measured for the G.
At $100 each, they aren't cheap, but to get rid of the 40mm fans in the power supplies is priceless to my ears.
What is the heat of the internal component like? I am considering buying the PC62, but if it doesn't reduce heat on the inside and therefore the 80mm fan on the heatpipe has to run like mad all the time then I might have to consider another solution.