Is a Weiss 204 DAC an upgrade, or sideways, from a Halo Audio Spring 2 Level 3?

Before considering upgrading from the Holo, try PGGB first, might be the only upgrade you will ever want: 

https://www.remastero.com/pggb.html#dacs

https://audiophilestyle.com/forums/topic/62699-a-toast-to-pggb-a-heady-brew-of-math-and-magic/#comments

Trained ears paired with a revealing stereo system should allow one to discern the difference, as demonstrated by the aforementioned gentleman.

In a blind level-matched test I doubt you would be able to tell them apart. 

it is not an upgrade and no, yoru DAC isn't bottlenecking your setup. @whyrichard 

Basically, this gentleman like Holo Spring better overall except for the soundstage.  The Spring has slightly less reverb and a narrower SS in comparison.  This is a bit counterintuitive, as the Spring is an R2R DAC while the Weiss 204 is an ESS-based delta-sigma DAC.

https://www.youtube.com/watch?v=7qCO1xWIObs

Well, as he also indicates, if you could save up and go for Holo May KTE, this won't be an issue.  Money talks in this case.