I use a RME DAC in my setup, and one of the things I like about it is the Bit Test feature. RME supply the WAV bit test files on their site. I've converted them to FLAC. The DAC shows up a message on the LCD when the bit test (played on repeat) is matched perfectly. So no stuck bits, missing bits, bit flips.. just the correct sequence repeated over and over again.

My FLAC files live on a SSD attached to a Raspberry Pi that serves them up over NFS. The data passes through three gigabit switches before arriving at another Raspberry Pi running Volumio, which is connected to my DAC.

There's enough there to keep an audiophile awake at night, but the bit tests have passed perfectly whenever I've run them. No expensive cables, linear mode power supplies, or audiophile switches would make the tests pass any better.