Dac methodology

Complex music is difficult for many systems to reproduce which is why the vast majority of audio manufacturers use relatively simple music for their show demos.  Even very high-end companies love Musica Nuda (bass and voice) Vanessa Fernandez (a few well-recorded instruments) and the like. IMO, if you want a system capable of playing complex music, you need to evaluate everything in your system and try different combinations until you are getting what you want.  Your stuff now is pretty good, so maybe your expectations are just not realistic within your price point.  BTW, I don't think a tube dac with a tube preamp would we "redundant" as you put it. I had the EAR Acute CD player with a Viva tube and and it was a great combination.  

It does not sound like a DAC issue, to me. Those are very good DACs you have.
Have you decoupled your speakers from the floor? That would make a big difference in SQ, like having new speakers. Try, also, moving your speakers away from the rear wall, a little at a time.
Good Luck.