After prolonged scanning of relevant forums and Test sides and opinions of colleagues who already have a NAS, I decided for the Synology. Interestingly, one can directly relate this from Amazon only via Warehouse Deals to Austria. What the hell, for it was then also cheaper.
Conclusion: Cheaper mass storage devices (4x3TB WD Red) makes what he is - my media (music, movie, photo) to store centrally.
How well the apps are offered (video station, ...) I can not judge, since the film access via Raspberry done.