The max volume of the headphone is really low, but the speaker sound is very loud. I mean, people actually asked me a couple of times to lower the volume of my 3DS because it was competing with the TV volume. Of course, the 3DS was not made to be a mini-stereo system so you cannot use it for a small friends reunion, it was designed to be used by just one person in a moderately quiet environment.A. Turning up the decibels ruins sound quality I doubt anyone would go beyond 125% out of 200%, And you must not own a 3DS because the "max volume" speaker or headphones is incredibly soft. Not fit for music playback, and personally, not fit for gaming.
About sound quality, the 3DS speakers really rock. It may not handle low frequencies that well, but for that size no device would. About the headphones, I don't found anything wrong except for the low volume. Taking that aside it work very well and if you get used to the low level of volume, at least you'll be sparing yourself from ruining your ear in the future. If you want exceptional sound quality, unfortunately we're stuck with low quality and high compression music files nowadays. So it doesn't really matter what device you use, you will be stuck with low quality music anyway. The best you can do is buy a vinyl player