[jaclaz]

Possiby not what you want to hear, but personally I have always bought (usually for peanuts) used (fanless) "thin clients" and added a PCI NIC, they make very good routers on the cheap, and since (originally) the machines were sold for lots of money to the enterprise market, they are generally very good quality/well built, sturdy, suffer not from overheating, etc. If you want to buy "new" there are several suitable mini-itx boards available.