Keep the Mac Mini.I have one and hate the MAC OS but you d not need to replace it to get great sound.
Read the John Swenson white paper on streaming. If you want to try his approach, get a media converter such as a Sonore OpticalModule, Uptone EtherRegen (use reverse), etc.. Then get a Sonore OpticalRendu to take the FibreOptical from the media converter int the OpticalRendu and then tale USB into the DAC.
If you want to save some cash for a slight los in quality then get a network switch that has a Fibre Optical output. Take the Fibre directly into the OpticalRendu and then USB into your DAC.
Fibre cannot carry analog noise like Ethernet can and pollute your DAC. I was under the impression that the very best method to stream was Fibre directly into a DAC (like Lumin X1 DAC) or second best the Sonore OpticalRendu. However, after reading John Swenson’s comments about adding a media convertor in front of the OpticalRendu I tried it and my tunes sounded even more focused so now I also do that for 2 or my 3 OpticalRendu’s.
Ethernet streaming is easier but most DACs do not have this and the DACs that I have heard with it sound better streaming via an OpticalRendu to the USB input of a DAC.
All the Rendu’s are ROON READY.