I use one and will not change. A 2012 Core i7 2.3 GHz machine with 16GB of RAM is an amazing music server when running dB Audio Labs software.
The USB port on the opposite end of the IEC power inlet is the one to use.
If you have not tried this simple, no cost SQ hack, do this:
listen to your favorite reference track.
shut the mini down and invert the polarity of the IEC C7 connector.
reboot and listen to that same track again without doing any system changes other than the PC polarity inversion.
report back with your findings.
other, no cost Mac mini tweaks may well be forthcoming if you all are interested.
What we don't know or understand about how to achieve the most gratifying musical enjoyment could fill a book. Most of it doesn't make sense. It just IS.