Point of diminishing return for a DAC

The DAC is not the problem, the server is the problem. The Mac Mini is, frankly, an atrocious server. I know, I used it for a while. One of the best moves I made in terms of digital sound was to dump the Mac Mini (even though using an upsampling program) and going to a dedicated audiophile streamer/server. I have written up three of them for Dagogo.com; Wolf Audio, Salk Audio and Small Green Computer/SONORE. 

As long as you continue to use the Mac Mini NO DAC will be optimized. That is not to say you could not see better sound from a different DAC, but it will be nowhere near the potential.  

Finally, if you are not using quality aftermarket cabling, i.e. SPDIF or USB, you are fairly wasting the potential of a DAC. 

That is your gift; Merry Christmas! 

Congrats on the new DAC! Recommendation: Try all permutations of gear and cables available to you. Do not be overly discouraged if some of the permutations with the old DAC as good as the new. That is the nature of mixing gear in systems. One simply has to try all permutations to know. 

You have now heard from several people who are telling you that the Mac is an issue, an impediment. Perhaps that should be the next move.