No moving parts? What about a cpu and psu fan? And maybe a northbridge fab?
Still possible with an Epia motherboard and matched case with external PSU unit (like laptops). Checkout the link:

http://www.ultim8pc.co.uk/index.asp?...products&idd=2

As far as the Mini-ITX / Epia mobo's are concerned, it's a matter of finding the fastest passively-cooled one available.

Outside of the Mini-ITX arena, there are a few full-strength passively cooled PSU's around, and you'd then have to look into heat-pipes or peltier units with external water coolers. Messy and a lot harder to spec and source - but the performance would be there.

HedRat