DAC with the best midrange ever.....

Who knows what the best really is but I can vouch that the mhdt Paradisea tube DAC with the stock GE tube is top notch in the mids.

The Manley Reference DAC from the mid-late 1990s. Check it out here. I have had one for several years and would not let it go because it does the middle 6 or so octaves like nothing else. And with the help of Steve Huntley at GNSC to update power supply caps and a few audio stage caps, this unit was taken to yet another level of performance, particularly greater extension on the top to allow those magical midrange harmonics to decay even longer. No other DAC that I have tried renders the piano like this. The all maxed-out APL Denon 3910 that I also own has a little more low-level detail and a little more dynamic punch in the lowest octave, and it is quite musical with the 7062/12BH7A tube, but the Manley continues to be the midrange king.

You should consider an Audio Logic DAC, I think it fits your description very well. Perhaps a little full in the bass compared to something like the EMM Labs (I use both in my system), but consistently natural and musical presentation.

Altmann Attraction DAC

It might be ugly and inconvenient, but it excels with music and has a very neutral presentation.