I just received a new base model 27" iMac and added a 512 GB ssd as an upgrade. I'm angry as I was assured (by 3 seperate tech guru's (yeah right)) that it would ship with HS but shipped with Sierra and as I spent so much, why should the first thing I have to do, is upgrade. My other issue is that when I go to about this Mac it says I have 500gb flash storage less the programmes i.e. (498.95 down to 466.85GB) my point is where are the extra 12gb with a 512gb machine and have I got the latest apple ssd's. these little annoyances haven't filled me with no confidence and wonder whether to send the thing back. advice pls ??