Upgrade from QNAP TS-670 Pro to?

Because QNAP stops the support (but today I’ve got a new firmware update) for the TS-670 Pro, I’m thinking about an update.
At least I want to have a NAS with i7, 32 GB Ram and six bays. I’m using some docker, web server, wiki, dlna server, bind server, ROON… and a lot of videos and music.
Prices have become really high for bigger and faster NAS and my knowledge in this area is a bit outdated.
So: for which systems should I look for?
It must not be a commercial NAS (I’ve no problems with setting up systems in Unix or Linux), but it must be a system, which spares energy and isn’t too loud.