I am using the Seaport Free Agent Go Pro 500GB external hard drive for my MAC Book pro to store my music files. I have a 2nd Seaport for backup. I have had no problems with either hard drive. I load all my music on the external hard drive. It sounds better if it is on a different controller than the DAC, which means a FireWire hard drive. The Seagate is a portable external drive and has a 2.5" drive inside it. The advantage of this over a bigger external hard drive with a 3.5" drive is that it will be much quieter and it will run off the power provided by the bus. This means you will not need an extra wall plug for the hard drive.
Please see http://www.seagate.com/ww/v/index.jsp?name=ST905003FJA205-RK-fa-gopro-mac-500gb-hd&vgnextoid=13530c1001c11210VgnVCM1000001a48090aRCRD&locale=en-US
Please see http://www.seagate.com/ww/v/index.jsp?name=ST905003FJA205-RK-fa-gopro-mac-500gb-hd&vgnextoid=13530c1001c11210VgnVCM1000001a48090aRCRD&locale=en-US