So - am I understanding you correctly if I think you say is you might want a colored/mid-centric DAC?
I haven't heard the Questyle, but tend to find most modern DACs to sound quite similar with regrades to sound signature - because - relatively speaking - they are all trying to be neutral. They vary mostly on detail retrieval and speed in the different frequency areas,but they mostly have a quite similar tonal balance.
FWIW - I guess what I am saying is that it is more effective to roll tubes, amps or headphones than a dac if the objective is to alter the sound signature. I'd say - if you have a great deal on a great dac with a neutral sound signature - get it and spend your efforts rolling tubes instead of dacs