My previous device was Xperia Mini Pro, i used to listen to music very well on that phone. Then I aquired the Xperia L and i was very dissapointed with the sound quality, very low power, the Mini Pro had more "abrassive" sound.
I don't want to make advertising or Spam, but this APP solved the problem, this "unleashed" the device real power. It's a Paid APP by the way.
The APP is called "Volume Boost" by Kibohely
Now it sounds the same as my previous Mini Pro.
I made an experiment and I installed the same APP on my old Mini Pro, but nothing changed when i activated it. This makes me think that the Xperia L and posibly other devices have their power truly "locked".
I don't know if there are any other apps doing the same thing, but this worked on Xperia L.