I suggest keeping your existing modem/router and adding either just a gigabit switch or alternatively a gigabit router if you can use improved wireless or some other functionality.
Adding just a gigabit switch is the simplest, cheapest, and possibly the best for the LAN feature set. Connect a LAN cable from the 2wire to the switch, and connect all the gigabit clients to the switch, and you're done, and also get more placement options and a higher number of wired ports.