I currently have an older iMac that I am doing some research on replacing. When I switched from a PC over 5 years ago, I was concerned about upgradability, but decided to make the trade off and get an iMac for the convenience of an all-in-one. Over time, my all-in-one grew and while I didn't have a separate monitor and tower, I now have an extra CD drive, USB hub and external hard drive. As I am now considering a 2015 iMac with an SSD drive, I would need, at a minimum, yet another external hard drive because my media that is now on my 2TB internal drive would not fit. What options do I have for multiple hard drives that would be cost effective, reasonably fast and take up the least amount of space and ports on the computer?