Changed my D-Link DNS-325 with minidlna to a Qnap TS231P. Did not know that Qnap changed from Twonkyserver (delivered with license) to an own model. But their house media server seems to be alpha or beta, have amnesia and dislike straight media scan. So i had to install and buy a Twonkyserver 8.4.2. Especially because some of my devices dislike FLAC audio or M4V video and the Qnap ms does not know to deal with it.
Twonkyserver 8.4.2 includes profile files for media receivers and media conversion files that can be edited, cloned and configured to detect a device and serve alternatives. Here as short tip i like to point at ffmpg video conversion that requires enough CPU power to do it on the fly, so buy an Intel device instead of ARMel types.
At all Twonkyserver give enough flexibility for me to solve curios devices in my UPNP environment.