There are means to get nice sound out of computers such as mac mini but requires much diy effort. I used three different iteration of mini's over the years, last one provided very nice sound quality, no complaints, could have lived with that one for a good many years.
I agree that general service computer does not belong in high end streaming setup, self generated noise, lousy rendering, nothing you do post computer will get back what's been lost in the noisy general service computer used as streamer. Stock mac mini is one thing, highly modified mini is quite another.
As good as that final mini was, my present streaming setup betters that by quite a wide margin.
My greatest issue with vast majority of off the shelf streamers is lack of processing power, forget about running HQPlayer or any intensive DSP, I bet many would surprised by what DSP can offer. Versatility of present setup allows great manipulation of digital bits, like having a number of different streamers and dacs in one system. I'd suggest custom build streamer is valid route for top flight streaming if one is up to the task.