It sounds more like you mean a powerline adapter than a broadband extender. A broadband extender plugs into a mains socket, picks up the wifi signal wirelessly and re-transmits it, so EXTENDING the range of the wifi signal. A powerline adapter also plugs into the mains but also has a cable connection to your router; a second (or third) adapter also plugs into the mains in a different location and has an internet cable connection to it. If yours is the second system it will work perfectly with the 600 model. On my system I have 500 units linked to 200 units with no problems.