Hi,
I remember in the past that there was a Ethernet Port Daughterboard, available that could extend the amount of 10/100 ports available on certain RBs… For the love of me, I cannot find any reference to this board either at routerboard.com, nor from any of the local suppliers. Has the board been discontinued?
Side Note: MT, why, oh why, can the 493 not have a GB port? 
8 x 10/100 and 1 x 10/100/1000 would make it SOO ideal hehehe