SSD Conclusions
I decided on what to do about the iMac harddrive situation mentioned in Finding a good Thunderbolt disk: I ordered a Seagate GoFlex thunderbolt adapter and caddy, containing a 1TB drive, which I'm going to replace with a 1TB Samsung 840 EVO drive.
That means that I'm not going to get the 550 MB/sec of the Samsung drive, but about 330 MB/sec where the SATA/Thunderbolt adapter caps out. I'm sad about that, and I'm also sad that I couldn't find a SATA/Thunderbolt 2 adapter at any half-decent price (not that anything Thunderbolt is decently priced, but I mean not ridiculously stupidly priced)
It was a toss-up between the Lacie and this one, but believe it or not, the built-in Thunderbolt cable came in as a minus for the Lacie, as I don't know how I'd go further if it would break. Also, the Lacie didn't disclaim what disk was in there. With my combination, at least I know I can move the disk into the computer or into another enclosure if it turns out I am really sad about the performance drop. I expect to keep the disk around longer than the enclosure.
So, waiting for the mailman to come, and dreading the stupid US/EU import-tax (I expect to be writing about that later) and taxing charges.