I bought an external desktop DAC/amp for a simple reason, I need enough output to power my DCA Stealth. My DAP does not cut it, it only drives the DCA Stealth to insufficient volume. Also, the DAC/amp connects to my laptop with a simple USB cable, which allows me to apply all sorts of DSP on my laptop prior to playback. DSP options for Windows is far more extensive and offer much finer control than my DAP.