I need to buy a complete system.

A lot of money and buying unheard..
My guess could be these speakers driven by Allnic electronics with the help of Purist Audio Neptune cables.
Another possibility could be Kharma speakers.

 https://www.audiogon.com/listings/full-range-jm-labs-utopia-alto-be-2017-11-30-speakers

Maggie 3.7i, 20.7 depending...
- drive them with a Benchmark AH2B amp (which can be returned!)

used ARC LS25 or 26 pre-amp

Benchmark DAC3 (or Schiit Yggy if Redbook only) (both can be returned!)

investigate an LPS for the Mac Mini (inexpensive)

isolation transformer for a few hundred $$

use the money I saved you on room treatments...

mhsmith,

     I like randy-11's system suggestion but I'd add the Swarm Distributed Bass System for good. natural and solid bass performance throughout your large space: www.theabsolutesound.com/articles/audiokinesis-swarm-subwoofer-system/
     You can then setup the Magnepan 3.7i or 20.7 speakers for optimum mid-range, treble and sound stage performance at your chosen seated listening position.  You'd still have plenty left for room treatments to dial things in . This could be a dream system that I'd love to hear.

Best wishes,
   Tim

I assembled a $20k tube/computer audio/TT sytem at the beginning of this year and could not be happier with the results. See my previous post for system details:

https://forum.audiogon.com/discussions/second-system-that-sounds-and-looks-spectacular-i-am-there

Harbeth M40.2 speakers.
The forthcoming DPSpeaker X4 preamp/DAC/room eq
Any beefy 300+ watt power amp
Oppo 203 disc player + nice tv screen to watch opera etc
room treatment to minimize reflections
upgrade potential: multiple large subs