I own the Xonar and the D18. I do not use the Xonar for anything other than movies. If you are wondering, I have owned the Xonar for a long time and bought it mainly for gaming. There is no comparison between the Xonar and the D18. They are on two completely different levels. The D18 is worlds above the Xonar as a dac for stereo playback. Do not place too much on the comments about the D18 sounding very analog. Those comments are meant as a complement.
Do you have the Essence ST/STX or another version of Xonar?
Is good to know the Yulong is superior to the Xonar.
What I'm concerned about is the smoothness of the treble. what I think reading this, is that there is a lack of treble, I don't know if this is correct. I'm new in all this things and don't know what exactly means.
With my other option, Violectric V800, my concern is the opposite, harshness in treble and audio fatigue.
I'm in an infinite loop like "Read about D18 and like it, read about the V800 and like it, read about D18 and like it, ..." and so on , with the opposite concerns.
I can't decide which one.
But for your comment I think any of them will be superior to the Essence ST, and it is a relief .