Upgrading my streaming/digital system- what would make the most sense?

Hello all,

I would like to improve my digital chain and I'd like to get your feedback on which component(s) are worth upgrading first.  I would like to get a more natural/organic sound and more naturally layered soundstage.  Don't get me wrong, it sounds good but there is a bit of digital haze ( I think the blacks could be blacker and spatial cues could be more present- thus the somewhat flat presentation), and at times the music sounds a little artificial, albeit very clean.
I use Roon to stream Tidal and Qobuz and the digital audio chain consists of ethernet  cable> switch (basic cisco)>  2 ethernet cables
> Macmini (roon core) 
> Moon 280d with Mind2 bridge (roon endpoint etc)
(The rest is Vinnie Rossi preamp in passive mode to Pass Labs xa60.5 mono's to Avantgarde duo's or Thiel 3.7's; cabling Nordost Heimdall 2; I also have an analogue set up).

I had always assumed that the most effective upgrade would be the dac, particularly because in this configuration the '"noisy" Macmini does no processing other than sending a stream of 1's and 0's as a Roon core/server to the Moon/Mind2 bridge as Roon endpoint/renderer.

But some have suggested that this is not the case ie the Macmini should be replaced with a Nucleus or Small Green Computer, or something else along these lines, rather than the Dac.  But would that really make such a noticeable improvement rather than a considerably better dac?
Or would something else yield a better improvement?
I would like to go in stages rather that doing a wholesale replacement of the entire chain so I need a bit of help to decide what the next step should be- many thx for your thoughts and feedback.