Point of diminishing return for a DAC

Thanks to all for the helpful and detailed responses.   All have helped.  I’ll post again once I’ve purchased and have had an opportunity to do some critical listening.

Again,
Thanks
Bob

I would strongly consider an R2R DAC. You won't have to spend anymore than specified and there are many out there.

IMO: The point of diminishing returns depends on how much money you have.

Get the MacMini out of the picture by buying something relatively cheap like the following.

https://www.audiogon.com/listings/lis9j9ee-sonore-ultrarendu-network-streamer-ifi-ipower-power-supply-roon-ready-21642-music-servers-docks

It is ROON READY. It is an Ethernet-2-USB converter. Some call it a Digital-2-Digital converter. I use the lower model, the microRendu, and it isolates the computer from my DAC. A used microRendu can be had for $400-$500.  

Computer Audiophile just named the Rendu products as the digital product of the decade. 

$2k for the Matrix XSabre Pro MQA DAC. Best measured performance on Audio Science Review out of 150 tested dacs.