So, I have a late 2015 5K iMac with a 1TB 5400RPM HDD and would really love to be able to boot from an SSD. I have a few questions I can't find the answer for, even when searching the forum etc. Will running my OS from an external SSD be better than the internal HDD I currently have? If yes - is there a preferred SSD & Thunderbolt caddy you would recommend? I have seen a lot of people suggesting this situation should be avoided and you should just get an internal SSD. I am a little weary of doing that myself - it looks so much more complicated than the non beveled design of iMac. Has anyone had any experience doing this? Does changing a HDD yourself void your warranty? Thanks for any help.