I have a 2011 iMac with only a SSD disk (250GB). I need to somehow increase the storage space. I could go with USB 2.0, but that is too slow. I could also get a Belkin thunderbolt extender that makes a usb 3.0, but thats just ridiculously expensice. So. Whats my best options? Does a guide to take out the dvd-rom and replace with a 3.5mm normal HDD exist? Are there cheaper alternatives to get USB 3.0 on a 2011 iMac than the Belkin and similar accessoires? I appreciate any help.