When to upgrade a router

I have been putting so much attention on what router I should upgrade to, from our existing WRT54GL (100Mbps ethernet ports), that I have ignored whether or not I even need to upgrade.

Currently, we have a 12Mbps connection to the internet via a DSL modem. This, in turn, is connected to our WRT54GL. Seeing that we have a 12Mbps internet connection, is there anything to be gained by upgrading to a newer router?

thanks

Keith