I owned this combination and noticed the Qutest brought more warmth and definition to the sound field. So I am surprised to hear your response to the change. I had traded a Rega DAC in on the Chord so I never really used the Bluesound direct to the preamp. However I did try a few digital cables before settling on the Kimber Kable D60 and have since upgraded to the Hugo TT-2
I’ll be curious to see if your assessment changes
good luck