Found a great deal (Craigslist) for an Airport Extreme Base Station, except this is not the new rectangular one that resembles Apple TV, but rather the older conical/egg shaped one. I'm wondering if this device- once connected to my wifi and to a USB HDD- will be compatible with Time Machine. Basically I want a Time Capsule without the cost. I know this works with the newer Extreme Base Station's, but I'm not sure about the older models. I do know that the seller says that there is a USB port on the device. Could someone shed some light on this?