I'm buying a 27"iMac this summer and need to transfer music and other files from my Dell Dimension E510. I been looking at External Drives. I found and like this one: OWC Mercury On-The-Go Pro Bus-Powered FireWire 800/400, USB 2.0 and 2.5" SATA Portable Hard Drive & SSD Solution However, I wasn't sure if this is the one best for my needs. My #1 reason for getting an external drive is for transferring files from the PC to the iMac. Second, to use it to back up my iMac. I see many options. My iMac will have 1TB+ 256GB SSD They have 2 models one with USB 3.0 alone another with USB 2.0 & FireWire 800/400. (Based on the iMac ports don't get the USB 3.0) I see 3 speeds: 5400RPM 8MB Cache 7200RPM 16MB Cache (believe this is the speed to get) like the iMac SSD My dilemma is the size I think 500GB is enough despite the 1TB HDD on the iMac even possibly the 320GB but there is only a 10 dollar difference $127.99 vs $117.99 So my final question is: Is this the right drive for my needs? and if so which size? Or is there another one altogether you recommend?