No one buys power amps to drive Susvara so they can listen at 130dB. That is not the point.
Susvara needs current to drive, a lot of it. And a lot of headphones amplifier can theoretically push a lot of power, but pushing a lot of current while maintaining quality is difficult task. A big chunk of headphone amps can advertise multiple watts of power, but the output becomes unusable way before the advertised limit. There ARE headphones amps that does a lot of current without compromising in quality, but the choices are not a lot and the price can be very expensive.
This is where power amplifiers come in. They are made to drive speakers, which requires a lot of current. Which makes it a perfect choice for driving Susvara on a lower budget. With a lot of choices on top.
The <100mW amp narrative only works in following few cases:
1. It's clipping but you don't notice it
2. Your "music" choice has no transient peaks, that's why extra power is not needed
3. You are listening at much lower volume than others, thus the extra power is not needed.
4. You are making stuff up
Please stop posting these low powered amplifier nonsense. Power is simple, if you don't have enough power, you don't have enough power. No amount of grounding, transport quality can change this. End of discussion.