Then at least the T+A DAC 200 or HA 200 is better in that respect than D-6. In both ways. Plus you get relay switched resistor ladder volume control if you like to skip preamp.
Gustard A26 is pretty good too (with the updated controller firmware) if you want to look at 20k band. THD harmonics peaking around -128 dB.
Multitone is nice too.
From subjective perspective, combine A26 with ASDM7EC-light modulator and you have “bass machine” 
. Although DAC 200 has more kick in it.