I’m just trying to understand why the volume is low. I don’t have any trouble with vero driving my mains stereo amplifier.
One reason for low volume could be the input impedance of your speakers is low. If that was available in the specifications it might give some pointers.
The DAC Extra Gain (when it does work) will cause clipping on loud audio. An alternative for video (but not for music) is to use Volume amplification in the Audio and subtitle settings. That doesn’t cause clipping but does cause dynamic range compression which is less objectionable.
Meanwhile, I’ll see if we can get that alsamixer setting back without causing other problems.