No.
Open iTunes, in the preferences section under one of the tabs you will find an entry field titled “library location” or similar.
By default it will be set to “C:My DocumentsMy music……”
Simply change it to //servername/media/Music
OR
Map the /media share on the NAS to a network drive letter. eg. Z:
Then in iTunes set the library location to Z:Music
That’s how my NV+ is set up. Firefly is used to stream music to the SoundBridges only
Your other two PC’s can access the library via Firefly if you wish but they will have read only access.
In fact it’s probably advisable to do this as iTunes like to “manage” the library and you don’t want all three PC’s trying to move things around