Thank you for your answer, ClieOS. I also hope I do not use excessive volume levels, but I really don't think so, since going for anything more than the mentioned 75% will really start to be too much. And as I said, the 50% setting of my player is a very comfortable setting I use 95% of the time without any issues (no ringing in the ears or things like that).
As I said, I was just a bit afraid that these earphones would require an amp, in contrast to others like the Atrio M5 which I also had considered.
So if volume-wise these two perform comparable, I think I will go for the AS6.
Kind regards,
nachttier