You need to save up for a Wadax. That is the only chip-based DAC that sounds any good,
You should write for Colbert.
My suggestions: Mac Mini USB to DAC probably isn't optimizing the SQ. Some aspects are theoretical but before you go and spend any budget on DAC upgrades I think you want to get your digital source(s) in order:
- You don't mention the source material - Tidal? Qobuz? Stored FLAC? Make sure you have some lossless material to use as a benchmark if for example you're listening to Spotify lossy. Caring about the provenance of the source material, both in terms of masters and file formats, can be critical to maxing quality. And this is probably something you can do without much up front investment.
- Consider getting a streamer and connecting by ethernet to your mac mini as a streaming server. Software like Roon works well in that configuration, but there are others. Streamers are just mini computers optimized for audio. You don't have to spend a lot to start - there are streamers that start at just a few hundred. Just make sure to get one with compatible DAC connections for your gear.
This will create a baseline for you to listen, audition other DACs etc. Don't just go and blow a ton of cash on a DAC upgrade (unless you really want a streamer/DAC combo), or if that's your plan at least get the foundation right so you can make good choices.
Also - just to throw this out there: speakers/headphones are by far the most influential in sound quality. Other things matter but doing that right is the best bang for the buck.