I'm running a 201x (can't recall exactly) Mac Mini that was modified for a linear PSU by Mojo audio. It made a HUGE difference in quality of sound.
The PSU has a split cable; one fixed cable powers the Mini, the other removable cable powers a 4TB AV HDD. From there, a TA Premium USB cable feeds a PS Audio DirectStream DAC, and then TA ICs straight to the amp. I have used an Off Ramp from Empirical (great piece of kit), but the jury is out on whether the DirectStream really needs it.
The Mini has been fully optimized for music (easy), and runs nothing else except basic system functions and WiFi so that I can control it from any Mac or tablet in the house.
I chose this route at this time because, if one knows a bit about Macs and isn't intimidated by some basic tech setup, it's flexible and pretty reliable. I've had very few problems, and nothing major.
Digital is changing quickly. Who knows what will come up even in the next year or two? Having my library committed to a portable HDD, as well as the ability to change the brain, protects investment. A dedicated server will likely be more difficult to adapt, and I would think one would be beholden to the manufacturer to provide improvements and upgrades (although I admit I have little experience on that side.)