Computer, software, USB cable or ?

Had some friends over for the holiday weekend and was playing a bunch of different stuff.  Started with some cable radio @ 48K via TOSLINK into my C50 DAC.  Sounded about as you would expect; good but not great.  Standard streaming, IOW.  Moved on to digital from my laptop via USB.  It's a MacBook Pro from 2012 with OS X 10.11.6 (El Capitan), 2.5 GHz i5 processor and 8 GB 1600 MHz DDR3 RAM.  I have the audio MIDI interface set to upscale everything to 32 bit 192 KHz so I can use iTunes as the file serving app for both standard and hi-rez files.  The USB cable is a decent quality computer cable, not an "audiophile" cable.  The sound was again good, but not great.  All files are ripped in WAV at source resolution (e.g. 16/44.1, 24/96 etc.). Bluntly, it just doesn't compare to my MVP 881 BR disc player.

I'm not expecting my computer source to rock my world, but I am wondering if there might be some way to get better performance.  Thanks in advance and I'll look forward to your input!