My computers are a 27 iMac (1TB hard drive) and a 13 MB (160GB hard drive). I have a 500GB time capsule which has filled up and a 320GB portable hard drive that Ive used for backups, but I am not currently backing anything up. I am looking to buy a large hard drive to do start backing up with Time Machine. Here are two options Im considering for backing up both computers. $150 - 2TB Seagate Expansion USB2.0 $140 - 1TB Seagate FeeAgent FW800 The price is similar, so it comes down to size or connection. I have no idea what the difference between the Expansion and FreeAgent line is. Any advice on what I should buy?