Just to clarify, you don't need to switch out your modem/router (unless you're doing it for other reason such as not wanting to pay the rental fee).
A quick simple solution is to pick up the Gigabit Switch. Plug you Pogoplug and computers into the switch. Plug your existing modem/router into the switch (like all the rest of your computers). Now you're on a gigabit network.
Yea but that old router I have only has wireless g, and as long as I have to buy something I also want wireless N. Not just want, I need the bandwidth. All I can get, and the better range.