There are many home and small office NAS boxes with built-in drive arrays and gigabit (or faster) ethernet. Quite a few are fanless too.
The wiki already has some details about the QNAP[1] and Seagate[2] devices that can run Debian. If you were buying a new one this week (Christmas present perhaps?), which would you choose and why? Or is there anything coming in 2017 you would prefer to wait for? My own personal preference would be a fanless device with the possibility of having 5 or more disk bays either internal or through an expansion chassis. Regards, Daniel 1. https://wiki.debian.org/InstallingDebianOn/QNAP 2. https://wiki.debian.org/InstallingDebianOn/Seagate/NAS