I really don't mean to sound like a dick. Hope the message won't read in such manner.
I don't think Samsung really is to blame for 3rd party audio being recorded in a very high volume.
I have that problem all the time, with MP3 files in my car. For some going from 1 to 2 is like for others going from 1 to 5. Minor adjustment make it way too loud, or way too low. I don't blame the car, I just adjust the volume using audio editing software.
I can't complain about my sound on the S4, the phone performs very well, in low and high volume. But I do open all my tones in Adobe Audition, and manually refine each to work perfectly for the specific device and their sound capabilities. I prepare 20 or so at one go, and they last me for a year, or more...