Required airflow for fanless Via's?

[cleverhandle]

My migration to rackmountable equipment has begun. First on the racking block is my router/firewall, parts of which will be arriving in the next couple of weeks. The unit will be built on an Epia 5000 with the fanless 533 Ezra and sit in a Supermicro 512L 1U chassis, powered by a DC/DC converter from mini-box.com. I'm pretty certain that everything will work out with a minimum of cutting, pasting, and Dremeling, but I'm not sure about airflow. The goals, obviously, are space-efficiency (a 1U chassis) and near-silence (the PSU and proc) - a tough combination. Now, the 512L comes with a blower fan that I assume is god-awful loud. Given that I have a fanless proc, no PSU inside the chassis, and only a single IDE drive, what are the chances that I can just ditch any fans entirely? The proc is rated for fanless operation, but does it assume some minimum amount of case airflow for proper cooling? And if so, can blower fans be run effectively at low voltage? I picked up a 40mm Sunon fan as well, just to have more possibilities to play with - maybe cut a hole in one side of the case or something. But really I'm not sure how this is going to shape up. Should be fun, in any event...

edit: added bonus linkage and fixed a typo in the mobo model