Quite a few Bricasti M21 DACs for sale cheap

If I am not mistaken, the M21 also has a third DAC - which is a one-bit converter for DSD streams. This additional DAC is ideal for utilizing the DSD output of SACDs as well as for converting high-resolution audio files downloaded from sources such as HD Tracks.

I think even the M3 has a one bit DSD converter which is selected by switching to NDSD option. That’s native DSD. You can toggle between it and the PCM. Or may be it’s implemented differently in M21. 

I hear good things about using either Roon or HQPlayer to convert all music to DSD, then feed it through the one bit converter on the Bricasti DACs. I find that almost always sounds great even when using regular Delta Sigma designs, so should work excellent with the one bit as well. 

Actually Bricasti doesn’t recommend upsampling before the DAC. I believe it’s in the manual. They’re of the opinion that the DAC sounds best when fed the original bitrate. I tried upsampling to DSD using Lumin U1 Mini and the built in network card as a roon end point using roon dsp. In both cases I preferred the sound when feeding the M3 the original bitrate.