The SuperMicro Atom boards are the best available at the moment IMO:
http://www.supermicro.com/products/nfo/atom.cfm
The single-core variant only has one NIC, but you can use a PCI or PCIe NIC.
They're not fanless, on my Atom 330 the temperature is pretty good, I bet I could even remove the small CPU fan without too much problem. Although it's not something I would recommend.
Maybe you could remove the small heatsink and replace it with a bigger one to compensate ...
As a sidenote, this site is running on the 5015A-H with an Atom 330, it works really well IMO and the price is also good. I payed about 300 euro in total, this includes two disks, power supply, casing. The single-core variant is cheaper.