In my comparisons, of my Schiit Stash, all of the Schiit Delta/Sigma DAC's have a similar sonic signature. Even and sweet, with great musicality. A natural analog sound. But, as you step from the Modi 3, to the Modius, to the Gungnir D/S, you gain in the details of the sound. More extended bass and treble, better timbre, and micro and macro detail, soundstaging, and dynamics. Deeper reverb tails, with a better sense of space. If you're happy with one, you'll more that likely be happy with any of them.
Now, I also have a Bifrost DAC, and I'm lucky (stupid) enough to have D/S and Multibit cards for it. Swapping in the Multibit card gains a more forward midrange response, resulting in greater midrange detail. Imaging is slightly better, though, I didn't find a huge difference here. Dynamics are better, with more bass slam, but at the expense of slightly more bass boom too.
Some like the Schiit Multibit DAC's the best. Me, I like the Delta/Sigma DAC's. Just so natural to me. Relaxed and easy to listen to, without fatigue. Not a blow you away DAC, more subtle, that draws you in. The Modius is a great example of the Schiit D/S DAC. A nice price point. A used Bifrost 1, with the 4490 card, is also worth looking for as well. All the attributes of the other D/S DAC's. with some of the bass slam of the Multibit. Another bargain, considering their used prices. Update-able, if desired?