NAD M51 upgrade


Been running a NAD M51 for a few years now and have been happy with the performance. I tried out a RME ADI-2 FS and found it too be too bright, and that it did not match the musicality of the M51. Any suggestions on a DAC upgrade? I'd like to spend <$2k. I'm using the NAD M51 as a preamp as well so I'd prefer a DAC that has remote volume control. Mytek, Chord and Metrum all seem to be highly regarded.
jeenam
Thank you for the tip on the Sonnet Morpheus. I think that and the Lumin U1 Mini will be my next upgrades.
One other comment. People seem to think that DAC's are the end all be all of sound. Let me remind you that Analog is still king in the studio world. Analog synths and effects gear using tubes (gates, compressors, summing amps) operate in the analog domain. The BEST studio gear is analog. Tape compression still cannot be duplicated in the digital domain. 
I recently replaced an M51 with the RME and I think it is a much better DAC. The M51 is no slouch but it simply is not as clear and intelligible as the RME. CLARITY, would be the word to sum up this DAC. Much better delineation of the lower registers too. It is not bright at all in my system , in fact it is perfectly balanced from top to bottom. The feature set is off the chart, its the Swiss army knife of DACs