I am interested in setting up a wireless network, and the new Airport Express sounds pretty nifty -- but I notice it is still priced $70 less than the older Airport Extreme base station. Despite the built-in modem, is there any technological advantage to the older Extreme base station. It does not have the AirTunes capabilities. Is it a superior Wi-Fi broadcaster? I just don't get what about it would warrant and older piece of machinery costing more than the new model. Is Airport Express essentially a replacement for Airport Extreme?