I recommend you try Audirvana Plus playback software, made specifically for the Mac. You can try it for free for a couple of weeks. Learn how to use it to turn off other computer functions that compete with the music playback, and dedicate some RAM to buffer the music stream. This may reduce or eliminate the clicking and give you an overall better sound.
You will probably feed a cleaner data stream to your Dragonfly via USB with this, and even a Nirvana-decoded analog feed direct from the computer will sound better than iTunes on its own.
You will probably feed a cleaner data stream to your Dragonfly via USB with this, and even a Nirvana-decoded analog feed direct from the computer will sound better than iTunes on its own.