PS Audio PWD II vs. NAD M51

I wish I could help the OP with an informative response but I am in the exact same boat. (I almost made the exact same post.) I am looking to upgrade from a Rega DAC and am considering both of these DACS plus the Chord Hugo.

There seem to be great values available right now for between $1k and $2k new or used.

Can't speak for the PS but my M51 has not only replaced my previous dac with great sound, but my highly regarded preamp as well. It is a very transparent arrangement. If you think you might want to go down the all-digital road the M51 is an amazingly good way to get there.

I have a PS Audio DS DAC on the way. Up till now my NAD M51 has easily beat the EMM CDSA SE (an $11,500 dud), the AMR DP-77 (complete with tube-rolling failures), the Antelope Zodiac Gold, and the Berkeley 1, among others.

The DS DAC just retired my beloved NAD M51.

I have both. They both sound great and would be happy with either one, but if I had to choose keeping one, I prefer the PS Audio DACII over the NADM51. The DACII has a bit more air, warmth and musicality.