Minimum wired router specs?

I have the Uverse High Speed Internet Power plan. The gateway router is a Motorola NVG589. I have a Cisco/Linksys WRT54G2 V1 wireless router upstairs, connected to the Motorola router.

When I run the http://att.com/speedtest on a Macbook connected to the Cisco router, I am only seeing download speeds of about 9.37 Mbps. When the computer is connected directly to the Motorola router (using the wire that usually connects the Cisco router to the Motorola router), Speedtest is reporting 5x the speed (about 48 Mbps). So my conclusion is that the Cisco router isn't fast enough to handle the Power plan's 45 Mbps speed.

So what are the minimum specs I need to be looking for in a router? Ideally a wireless router with 4 LAN ports.

The Cisco/Linksys specs say the wired ports are 10/100 ports, and so I assumed that the 100 part would handle what the Motorola router is sending it, but that doesn't appear to be the case (why not I wonder?) So that would mean I need to get a router with 1gb ports?

Any help appreciated.

jd