Hi ppl.
Recently joined the Qutest team!
Acquired myself one used for 1025 euros.
And tried feeding my HD800 straight out using digital volume in foobar. Have A-B with Mojo. And i can confirm that the analog stage of Qutest is more than capable of driving a 300ohm load.
And oh i like the transparency over Mojo!
I do guess adding an extra cap close to the 5v power inlet would give benefit cause of the more current being drawn specially for the peaks.
I'm also sure it works better with high impedance HP over low ones, its just the law of ohm: power is voltage x current and higher impedance use less current for the same power, so better for the op stage.