Which DACs are known to be sweet/rich/relaxed?

I’m going to re-iterate that changing your front end streamer is most likely to take away the edginess with your existing excellent DAC.

The aforementioned Grimm MU1 is my favourite for achieving this and it’s all in one box with the Roon "NUC" included in the tin (so you don’t even need to worry about finding a separate Roon Server).

It’s a stunning piece of kit.

Someone mentioned earlier that they replace their dCS stack with it.

One of the BEST for the money = Chord Qutest

And if you want to spend RIDICULOUS amounts of money = dcs Bartok

I really loved the Aqua audio la scala dac.  The roon player was a lumin, I don’t recall the model, their entry level.   I would describe the sq as sweet and relaxed, like a fine Italian dinner and wine pairing.  If I wasn’t closing in on retirement,  would swallow the cost.  Currently using sonore ultra rendu player and audio gd r7.  Combined 3700 dollars.  I call it my high quality knock off.

Going back to the suggestion of cables - I can really recommend Sommer Epilogue, XLR or RCA.

It’s a really high end construction, but bargain price. It really helped me achieve a smoother & richer presentation, but still just as detailed. The change was not subtle. Epilogue is used in High End studios and also with B&W for their testing for 802D speakers etc.... so really worth a go for the cost of entry.

I have had the Mola Mola Tambaqui in my system and this would be my suggestion before you consider switching DACs.

"sweet, rich, relaxed"

I don't think these characteristics are likely to be found in a digital system.  Perhaps in a very high 64/256 recording, just maybe.

The DAC is the bad elephant in the room.  Every time you think you have a good digital recording the DAC goes and spoils it with dither and clock errors that cannot be rectified.

Once you have converted actual sound to digital there is no way back.