http://store.netgate.com/APU4.aspx with pfSense will walk it in and provide a reasonably powerful system for the price - $350 or $499 with pfSense pre-installed and ready to go.

Or buy direct from pcengines (will require some DIY building and seem out of stock for a couple of months frown ):
http://www.pcengines.ch/order1.php?c=4

and install pfSense.

The Alix boards would be capable too.

Any DD-WRT capable router will be capable (and cheaper). As mentioned it might just need some scripting.
_________________________
Christian
#40104192 120Gb (no longer in my E36 M3, won't fit the E46 M3)