Is it that bad really? IDK... Maybe those stats are fake? I searched for the stats on Google and found it.
http://www.jack-fi.ro/produs/asus-essence-iii/
There are also reviews here:
https://www.head-fi.org/showcase/asus-essence-iii.20083/reviews
"
Pros - Smooth and organic presentation, decent HPO, very decent DAC, functionality"
"I've heard my good share of $1K/$2K/$3K DAC's by now, and the E3 sure didn't disappoint"
They also have the highley regarded internal STX soundcard in the bottom of the same series. This amp was the DAC flagship model. The STX is only 200 USD but has generally respected sound which should be quite some "bang for the buck". The Xonar Essence STU is pretty much a DAC version of the STX, it has some more inputs/output options and can act as a preamp for 100 USD more. Lots of people also respect and appreciate the 700-800 USD Essence ONE Muses edition which is also a step under the Essence III.
Headmania has another review:
https://headmania.org/2014/05/30/asus-xonar-essence-iii-review/
This is not a poor 500 USD DAC/AMP.... It's at least a worthy competitor to Oppo HA-1.
Also things like implementation etc. are important. Not just stats. I was in touch with a respected Hi-Fi store that sold i.e. Quad but not Asus or Hifiman. They told me the voltage should probably be enough and sound-wise it could be at least minimum of it's potential.
You guys don't agree a 1500 - 2000 USD amp/dac that is enough for HD800 would be enough/fair for Susvara?
Yeah... Sure. McIntosh MHA150 might be good as well. I looking for minimum requirements, something to be at least OKAY. You can always say the McIntosh MHA150 isn't fair because a 59 000 HE1 or shangri-la amp is a must have. I don't looking for something optimal, just a fair, cheapest possible solution for not wasting 7000 USD. And cheapest solution is not a mobile output, it's something where it could be reasonable but cheap budget match.
You get the idea. Right?