Hi, I'm in the market for an external HDD for use with the new Airport Extreme's AirDisk feature. Ideally, it needs to be 500gb and (if possible) have the ability to automatically shut down when not in use. (Is this feature even available, especially as I will be running it from a poweed USB hub????). I've seen this on Amazon, anybody have any experience? http://www.amazon.co.uk/Western-Dig...a_3/203-3004487-7855929?ie=UTF8&s=electronics Thanks in advance, Steve.