I bought a QNAP TS-541+ NAS. It came with 8 GB RAM and I added an 8 TB hard drive and a 500 GB SSD.
After downloading the QFinder tool the NAS configured itself and finally showed this Web interface.
![desktop](../_Media/desktop_med.png)
The interface is quite snappy and works really really well. In fact I haven't seen a Web interface as well-done as this ever before. (Citrix XenApp comes close but is not nearly as pretty.)
![controlpanel](../_Media/controlpanel_med.png)
So far I found you can create users and groups, shares (SMB, AFP, and NFS), and an FTP server. The NAS also acts as a Web server and can be a VPN server or even a (apparently Windows-compatible) domain controller.
Each user has a home directory. Only the "admin" user can log in via ssh (or Telnet, if enabled). The su and sudo commands are missing.
![storagemanager](../_Media/storagemanager_med.png)
The NAS also supports the creation of virtual machines. I think it uses KVM.
![virt](../_Media/virt_med.png)
There are a lot of apps and features I didn't even try or look at yet.
So far I recommend the device fully.