Worth upgrading from a Grace SDAC Balanced to a iFi Zen DAC?

I’m seriously considering it for my SMSL SP200, for both the addition of MQA and the addition of a lighter amp for something like IEM?

I think if you plan to use mqa and want a bit warmer signature I think it’s worthwhile imo. I don’t know if I would recommend it if you are looking for a large jump in performance for pcm, but if you wanted to use mqa it makes sense imo

The Zen will also likely tame the SP200’s treble a bit. But as @M0N said, this will be an overall lateral move that will give you some extra features and different, but not overall better, sound.