I agree, i don't think I can use the h1288X unless I know it supports Unraid without issue. I never would've thought QNAP/Synology type device would suit my needs but the above two devices are very high powered in a a very rare chassis format (i.e. literally you cannot buy this chassis format right now until UNAS comes back in stock). That's why it's so expensive, there are no good competing alternative products freely available.That thing is a real 180 from what you were looking at building.
- It is very expensive, even considering what you get with it
- You'll be lucky to find one for sale (they appear sold out/unavailable in many places)
- It runs QuTS, QNaps proprietary OS. There are apps and such for it like Plex, of course, but you are limited to them, their update schedule, etc. It also supports Docker/LXC so it is flexible in that regard, though the Qnap forums indicate some level of compatibility/other problems with that setup.
That isn't a box that's meant for BYO gpus, etc. You go with what it supports. It's an appliance, not an open ecosystem you can easily customize. Think about things like spares for power, etc. - the power supply in that, from the looks of it is proprietary; how will you replace it if it goes bad? Etc.
Not saying it's a bad idea, just that again, it is nothing like the BYO approach you were looking at and has a different set of pros/cons. It is a nice form factor, which is the advantage of going custom design like Qnap did for the motherboard/ps/etc. but on the con side limits you to their supply chain if something fails.Etc.
QNAP direct has both in stock it seems, the 1288X with 16GB ECC (2*8) for $2000 and the 12-bay 1688X with 32GB ECC (2*16) for $2400 (latter actually seems like a better deal).
The power supply has connectors for GPU and 550W should be plenty. QNAP has the space for a dual slot GPU as well as two x4 devices (and comes with 10GBe vs. I've been worried what I can jam into the 810A's two ports), so it seems pretty decent from a compatibility standpoint.
Again - this really hinges on unraid compatibility as last thing I want is buying a server for next 5-10 years and being locked in a shitty EOL supported mfg'er OS.