Well, you come to the right place to find out to do with computer. First we will look at the economic way to improve sounds.
Hissing sounds come out of speakers when they are turned up too high.
So with this, you could get better audio sounds. Well, maybe by luck that you don't have to buy new ones. If you are still not happy, use the mp3 player's equalizer. With Winamp, you can use your own equalizer settings. It is even better if the speakers point to you and at the same distances away.