I had a very good listening session yesterday with the Dangerous Source + EF-6.
It's still too thick and the bass is too present but things are getting better. I could well imagine keeping them in the end, but I would need a silver cable and sell/exchange my SA-2 for something brighter (NFB-27 / Master 7).
Before that last session, I was 100% in agreement with TheDuke findings (overpowering and bloated bass that results in a dull and thick sound. One cannot say the Chord or the SA-2 are bad DACs by any means, so quality is not the reason here; tonality matching most likely is).