Listen to what
@solderdude is telling you. 1.2db increase in input from the Loxje may not be enough to sound louder to you. You may feel like the Khadas and the Loxje are the same volume. But that small decibel volume increase will result in the audio sounding
better because it is slightly louder.
That being said, if you want to ignore the role that slight differences in volume can make in perceived audio quality, then all you need is an accurate DAC with higher output like the Loxje. Then your tests will make it sound better compared to the Khadas. Not sure which one does that, but someone else can probably tell you.