If all you are going to do is connect the N-50 to your network (either by wire with an ethernet cable or by WiFi with the AS-WL300 wireless module), ie, just so you can use the Pioneer ControlApp with your USB HDD still connected to the N-50, then it's not going to make any difference. The Pioneer ControlApp is just a substitute for the stock remote control. Also, the Pioneer ControlApp doesn't even have all of the remote control's functions, as you can only use it to select and control the N-50's inputs (so no advanced setup functions, etc).
If you really do want to speed up browsing and selecting your music files for playback on the N-50, then the only way is to get the music files managed by UPnP/DLNA media server running on another networked device. The UPnP/DLNA media server uses an internal database to manage the music file library, allowing browsing via music categories (such as album, artist, genre, etc), so long as your music files have been correctly tagged with data matching those categories. My recommendation for a UPnP/DLNA media server is the excellent free music file dedicated MinimServer:
You could use a networked computer to run the UPnP/DLNA media server and either attach your existing USB HDD to it or copy its music files to the computer's own hard drive. This does mean you need to make sure the computer is switched on every time you want the N-50 to play those music files. That's why some people prefer to use a low power network storage device instead of a desktop computer or laptop, that can be left on 24/7 to run the UPnP/DLNA media server, such as a NAS (Networked Attached Storage).
You could even, if you are ok with a bit of (minor) DIY, run a UPnP/DLNA media server on a tiny low cost, efficient & reliable networked computer such as a Raspberry Pi. It's quite straight forward to install MinimServer on a Raspberry Pi and attach a USB HDD to.
The N-50 supports accessing UPnP/DLNA media servers over the network for playback of their music file libraries in two distinct modes:-
1. As a Digital Media Player (DMP), aka 'pull' mode, where the N-50 itself is doing the browsing of the UPnP/DLNA media server's music library via the N-50's Music Server input. So either using the buttons on the box or the stock remote control or the Pioneer ControlApp. In DMP mode the N-50 supports gapless playback. However, the N-50 as a DMP provides a very basic user interface to access the chosen Music Server with:
you can only navigate via the music library's music category folder structure;
it doesn't provide the ability to search individual music file tracks;
the current playlist is always the set of music file tracks at the end of the folder stucture that you've navigated to;
it doesn't allow you to build a playlist using tracks across different folders;
it doesn't allow you to save playlists (nor therefore retrieve previously saved playlists);
no album art displayed on the Pioneer ControlApp, only on the N-50's onboard display.
2. As a Digital Media Renderer (DMR), aka 'push' mode, where the N-50 is told which music files to fetch from the UPnP media server's music library by a third party app that supports being used as a UPnP/DLNA controller, aka UPnP control point, aka Digital Media Controller (DMC). Unfortunately, the N-50 doesn't support gapless playback in DMR mode. However, depending on the chosen (third party) UPnP/DLNA controller app, you'll get a much more sophisticated user interface compared to the Pioneer ControlApp/stock remote control with the N-50's screen, which can include:
ability to search for individual file tracks;
ability to build a mixed playlist, using tracks from any folder;
ability to save playlists & retrieve the saved playlists;
album art displays.