You are incorrect Jack, I believe you are misinterpreting posts.

MD600 + MS600 + iPad works just fine.
The MD600 is both Store and Core.

Going back to your original post.
Originally Posted by JackD
Is it possible to connect a Media Source 600 to a QNAP NAS-Server and use an iPad for controlling it?
No because there is no Core with this combination, an additional device that is capable of running a Sooloos Core is required.

Have a read of Sooloos Components page in our wiki for more details.

Regards,
Carl

861v6+ID40, HD621, 8000.2, 7200HC, 7200.2, SKYQ Silver, PS3, PDP-LX6090, QNAP TS870-Pro (8*6TB), Roon, iPadAir2.
[In Reserve] C15, MD600 (2*3TB), TwinStore RM (2*2TB)