It's a tough job to please a woman
Indeed so! After finding not enough distortion I turned to power supplies and realized I now had two TL431s in series with this design to get lower noise. So I wondered if there was some kind of interaction between those two shunts and added a damping 220uF capacitor across each and invited wifey for another listen. This time she didn't notice the imbalanced sound/distortion on piano. Hmm, that's progress
The last step is - remove those capacitors and see if anything changes. What do y'all think the result will be?