The Pioneer N50 is a DLNA player, right?
If so, then in order to send music to it from MC you need to set up MC as a DLNA Server, and also a DLNA Controller if you want to use MC to control the playback rather than using the N50's interface.
To do this, go to Tools/Options/Media Network and enable the checkbox "Use Media Network to share this library and enable DLNA". I think that will generate an Access Key but this is not relevant for DLNA. Then go to Advanced and enable DLNA Server and DLNA Controller.
Then the N50 should appear in MC's Playing Now list in the left hand column. If it doesn't, give it a couple of minutes, or restart both MC and the N50. This effectively makes the N50 a "Zone" in MC terms and to play to it you need to select it in the Playing Now list (or you can use Send To... when right-clicking on a media file).
Note that if you're using another device to browse the library, e.g. a generic DLNA Controller app on an Android or iOS device, or using the N50's own interface, the streucture of your music library will be displayed according to the structure set up in "Add or configure DLNA servers" from the Tools/Options/Media Network menu, which you can customise, and not necessarily as you see them in MC's standard view although you may make them the same if you want.