I haven't heard from Rossmann yet. If I don't get a reply by Wednesday, I'll voice call them.
I did order the 6-bay Terramaster, which should be here tomorrow. If/when I'm satisfied it's running as advertised, I'll rebuild the pool and copy over what I can. Assuming everything goes smoothly (har har), I'll reinstall everything and restore from config backups, which I've been holding-off on doing until I can figure things out.
I really, REALLY hope the Terramaster "just works". Since it only accepts six drives, the power demand should be a lot less than the Sabrent. I'd still like to disassemble the Sabrent to see what sort of PSU it's using. I'm 99.9% sure it's something custom, but you never know until you actually eyeball things.
I'll report back in a few days. Wish me luck.