I had the same issue but fixed it. All my volumes was set to 100% and still it was very soft.
What you needd to have a look at, is alsamixer. it is a program you have to run in a new terminal window. set the main volume to about 75%. If you set it higher than this you will loose quality. let your amp do the rest.
You can set every thing from there. Gain, bass trebble etc etc etc...