I’ve heard good things about iFI Zen except the subpar interface and poor customer service. My comments about N100 was in the context of you considering DAC upgrade. The N100 is now 7 plus years old compare to newer, improved Pulse series. As good as is N100, I am reluctant to recommend due to its age and USB only output. I would’ve mentioned Aurender N150 along with Pulse but N150 only has USB out which again limits your options. So if you’re considering spending <$3500, Pulse or N10 despite of his age makes more sense to me.
If you can stretch your budget, consider Aurender N200. It would be a one and done purchase. As far as user interface, both Innuos and Aurender offers superlative Apps. I would give a slight advantage to Aurender Conductor App based on longevity, remote troubleshooting and excellent customer service.