I too have the MOON 280D MIND2 streamer/ dac feeding a REGA OSIRIS integrated amp, and driving my Brit speakers (HARBETH)
As you said, a warmer but still airy and very detailed audio presentation was missing.
So I replaced my entire NORDOST FREY cables array by swapping in a full CARDAS CLEAR cables loom.…… - Terrific upgrade …my quest was solved in spades .
Highly recommended.
- NOTE: Balanced (XLR) CARDAS CLEAR interconnects for the 280D as the source were preferred over RCAs
FWIW …