If you liked the Khadas Toneboard, the designer (Ben1987), has started a new company and is selling two new DACs. The one closest to the Toneboard but now with XLR balanced outputs is the Soncoz LA-QXD1 Balanced DAC. It sells for only $199 and is available from Amazon, etc. Measurements are even better.
Check out this AP measurement screen capture of the the LA-QXD1. Look at the THD+N measurements (lower right corner). These are superb numbers and even more amazing for a $199 DAC!
In the latest Stereophile, John Atkinson, is quite effusive in his praise of the $10k Weiss 502 DAC:
The Weiss DAC has a bombproof output stage! Intermodulation distortion with an equal mix of 19 and 20kHz tones at –6dBFS was similarly very low (fig.12), with the difference tone at 1kHz lying at –115dB (0.0002%) measurements