Headphones

Something to remember is that to avoid clipping you want something that'll handle the loudest peaks in a song, rather than the average volume. For music with high dynamic range, this could be as much as something like 25dB higher than the actual average volume. So if you want to listen to something like classical and occasionally like to be able to push the volume loud to like 90dB, that means you might realistically want an amp capable of driving your headphones to 115dB.

And that's if you're not touching EQ and only listening stock. If your EQ has a +12dB bass shelf or something and -12dB of preamp gain, then now for the same situation you want your amp to be able to reach 127dB. 127dB takes a little over 4x as much power as 120dB, so if 1W is enough for 120dB, you're looking at a little over 4W there.

So it's not completely unfeasible to need that much with that combination of power hungry cans + listening loud + high dynamic range music + EQ. Realistically though I think most people over-estimate how much of that headroom they'll actually need. Plenty of people listen to music with no more than say 15dB of dynamic range, listen at more moderate volumes, don't touch EQ, and then still buy a massively overkill amp thinking they need the extra headroom.