How has your long term experience been with this setup? I have a late 2013 base model 27" iMac (quad i5, 1tb spinner hdd, 24 gig ram), and I am interested in adding an SSD. I have read that a USB 3.0 enclosure will be adequate for adding an SSD, but TRIM isn't supported over USB 3.0. I've also ready that quite a few people have bought a thunderbolt enclosure and attached it to the back of the iMac base. I am looking at a Samsung 840 evo 240gb SSD, and I am completely lost as to which SSD to get. I've seen conflicting stories as to whether or not an external enclosure with its own power source is necessary or not. I am just curious as to the long term experience of the external SSD setup as a boot drive? Have any of you experienced serious problems with this setup? Also, could you please provide which SSD you are using and which external thunderbolt enclosure? Thanks in advance ladies and gents.