Amplitude (the thing you crank up) is only half the story.
Having 500V is a huge potential for harm, just like a dam full to the top with water.
But only when opening the flood gates you get flow. 500V and 10A is A LOT of power.
Power P (in W) = Current I (in A) x Voltage U (in V)
P = U x I
Ignoring RMS for now, that is a can I am not willing to open now.
Supplying the current (overly) simplified is what enables the driver in a headphone to reach the amplitude (volume) you dialed in.
Would you mind giving them a 3 liner review over here? I am unsure if I want them.