Definitely need to try a different source. Using the e17 on +6 with the shure srh840, 35 is good for me, maybe a little louder than needed. That's why I'm saying its weird, +12 gain on the he400, I can listen at 50 easily, and its not ridiculously loud. My hearing is fine, I know that for sure, I do like music a little louder I will admit that. I'll try again after work and see if I still feel the same.
Are you using the E17 through USB to a computer? When I used it with my iPod it was a lot quieter than through USB at the same volume setting.