Hello S,
No problem.
I am also learning everyday, so there is no need to be sorry about.
Regarding the matter, it seems strange if you don't have any other media players for audiophiles like Pure Music, Audirvana+, Amarra, Fidelia, BitPerfect, and alike, because if you do, it will fight over the audio device against JRiver MC. These players control the audio device exclusively (which some call "Hog mode"), so either they or JRiver MC need to be closed to play music by your preferred media player, but iTunes doesn't by itself. iTunes will just pause playing while JRiver MC is playing. I moved onto JRiver MC because there are inherent UX and playback problems in them because most of them started out as iTunes integrations, but that's another story. So, please check there are any other application controlling the audio device exclusively opened.
When I set Mac mini audio set up, I use DAC just dedicated for JRiver MC and set OS X's default sound output as built-in output and have either a receiver or speakers hooked up to the built-in speaker/optical output since I don't really care about the sound quality of sounds for the daily use (i.e. an alert, Skype, or whatever), and I'd rather watch movies in Dolby Surround or DTS, so hooking up a surround capable receiver using optical cable really helps.
I understand JRiver is currently developing WDM-like driver for OS X as well that lets other applications to play sound through JRiver MC. Once that happens, I am sure it will definitely attract more people to JRiver MC.
I hope this helps.
Best regards,
Y. G.