I have the Audio Mirror Tubadour V and was drawn to it because of the tubes. I dont have any experience with any of the others but the Holo Audio May KTE was on my short list as well. After reading about the tubadour..it just tripped my trigger. Vlad the owner is very accessable and answered my questions and was a dream to work with. I am sure if you reach out to him...you will be impressed...he knows about other dacs and may be able to answer comparisons on some of them.
What impressed me was the quality of parts used. Lundahl transformers, Vishay resistors,GAIA isolation feet, Furutech gold IEC inlet, built-in USB re-clocker..just a lot of attention to detail.
Needless to say I am a very happy camper.