Yeah I just discovered the Supermicro unit myself. Fanless wouldn't be an absolute requirement as long as the unit is quiet. This application is going to be for a small office and the computer equipment will be nearby. As long as it's "very quiet" and shelvable I can live with it. Having SATA is great. It would be nice if the rack mount brackets were removable, oh well.
I found these just now too. They are pre-built boxes, but complete units still.
http://www.applianceshop.eu/