You may want to try adjusting the Ethernet connection at either or both the 2-Wire and AEBSn to see if you have the optimal settings between them.
For the AEBSn, you would use the AirPort Utility and adjust the "Ethernet WAN Port" setting that is located on the Internet Connection tab of the utility. By default it is set to "Automatic (Default)." I would suggest trying the "1000 Mbps/Full Duplex" setting instead.
You will want to find the similar setting for the 2-Wire router assuming it has Gigabit Ethernet ports.