Best DAC for my system?

I'll second the recommendation of the Pro-Ject Pre Box S2 Digital. I have one in my office and think it's exceptional for the $399 price. I've compared it to the Bel Canto DAC 3 in my main system and it's close. It's also a very good preamp and headphone amp and won an EISA Best Product of the Year award for 2017-2018.

Yes, spend more.
No. not a fortune.
$1,200 will do it.
Buy used.

Benchmark 2 or 3.
Chord Qutest

Worth it.

Spend a bit more for a MHDT DAC, R2R, non over-sampling, no digital filter, no op-amp with a Tube :)

I have created a separate linear power supply for my Khadas tone board generic edition, and I bought a Nordost USB cable.
Well... this combo greatly improved the sound quality of the Khadas.
I have done 2 blind listening tests with friends, against the Schiit Gungnir and the Denafrips Ares II.
Nobody, I mean nobody was able to identify the Khadas. LMAO.
So clearly the winner is the Khadas tone board generic edition if we compared the sound quality and money.

Have you tried the DAC on the MX119? That would be the first thing I’d try. If you still feel you need an external DAC, I’d suggest upping your budget, plus consider used.