I've had a good experience with the last two. I chose them because they accept bitcoin (and orangewebsite is owned and operated in Iceland). If you go for some of the lesser known hosts, they will be flexible with what OS you want to use, especially if their platform is KVM based.
How did you set up the FF sync server? I just did a quick search and I think the instructions I've found were mostly outdated. Do you have a link or a name for the port?
I also enjoyed hetzner for a while and if I'd want a ZFS install I'd probably go with them as it's definitely very nice how they do it. But as I've just previously commented I found a slightly better price for my minimum needs with vultr.com (5$/per month) and ZFS is not important to me on this box.