The detail in love ...

The casing is very solid. The design is, as always, a matter of taste.
Personally, I could have on the "Tiger", at the top, without! In my opinion, does not fit this "logo" appearance of Essence One.
Another point of criticism is to be found on the front. The plastic buttons act, compared to housing, inferior. At least the ON / OFF switch could have missed an aluminum shell.

- Function

To use the Asus Xonar Essence One, the supplied driver software must be installed. This also recognizes which driver version is installed, and the firmware version of the device and the audio chip.
The volume controls are rasterized, however, be missing something of precision. The jumps, the switch of a screen are too large.
Fortunately, neither sounds intermittent power on / off, even during operation.

- Special feature

The additional volume control for the rear outputs, is a welcome addition.

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Now to the essence, the audio quality ...

First, the conditions:
I'm only on the quality of the Asus, as DAC and headphone amplifier, a.
For this purpose a Beyer Dynamic T 1 is used.
As with my headphone comparison, I used FLAC files primarily.

- Sound

The Asus has a relatively well-balanced sound.
Unfortunately, there is an exception: Instruments are placed partially to strongly to the fore.
The Asus is indeed dominated represent those instruments in great detail, but their dominance partly annoying.
So it strikes me that I have to listen to certain songs very focused in order to separate the voice from the instruments. This experience I had so far, make no other KHV.
The stage falls right out wide and airy. The separation of the instruments succeeds very well, but has the airy style of play also its downsides. Some instruments and male voices it lacks some momentum.
Women's voices sound contrast beautifully silky and light.

- Conclusion

Overall, Asus delivers a great performance.
Anyone who sets high on details and this would have presented with absolute precision, is well served with the Asus. Only the dominant instrument for representation and the partially airy presentation could deter some prospective customers.

- Alternative proposal

Lake People G109 / Violectric V100

So far my favorite!
Similarly detailed as the Asus, but with more drive and more balanced representation of instrument. The bass is dry, defined and has more pressure. The stage is set slightly narrower, but not cramped.

Note for G109 / V100: It's pure headphone amplifier. Therefore they have no built-in DAC section. When V100 but this is retrofitted.