I had the chance to A/B today against the Xonar Essence STX (/w LME49720s) for an hour in a quiet listening environment.
I think overall the ODAC is a step up from the STX's DAC.
ODAC is clearer sounding in the mid frequencies and lets more of the recording's details through. As such the sense of ambience in recordings is enhanced.
I think it is a question of the brain getting used to it, but absorbing more information from the mids tends to create the illusion of lesser bass presence in terms of quantity. However, when tested with bass notes, the ODAC clearly has no deficiency. In comparison the STX sounds like the sound has more body, but it is muffled.
The ODAC's highs are the biggest improvement over the STX. They just seem more realistic on good acoustic recordings - clear, extended and with remarkable resolution. In contrast the STX is harsh and sibilant at times.
I wouldn't say the STX sounds bad, but the ODAC seems to offer better fidelity. The differences weren't night and day, but obvious enough to be clearly noticed in a short listening session.
I also noticed that the ODAC did produce a high-pitched noise when connected to a switched off desktop PC. Strangely this doesn't happen when connected to my laptop.