Before upgrading your DAC, do you currently use your SM with its stock (wall wart type) power supply?
In my experience, moving to a Dynamo or at least a regular Paul Hynes (current SR4T much better than older SR3) power supply would significantly raise the bar in terms of refinement at the DAC output, actually quite shocking in my setup, as well as using a coax cable that does justice to the extremely short rise times of the SM spdif signal.
Enjoy the quest,
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