Can someone please guide me through what external solid state drive I should get for my mid-2011 27-inch iMac. It's starting to get sluggish - I have 480GB free on a 1TB drive (3.1 GHZ i5 with 12GB ram) running on El Capitan. There seems to be so much conflicting articles on what SSD works and what doesn't. I'm confused... will a USB 3.0 work with the 2.0 ports? Is Thunderbolt SSD better and what would I need to hook up one? I want to boot the OS off the SSD and maintain the iMac HD for storage mainly for videos and personal photography. But articles with TRIM, SATA, etc just confuse me. Can someone recommend a setup and/or solid state drive to buy (hoping to go with at least 500GB drive). Thanks in advance!