Drop your PCM mixer value to ~90%. You are probably getting a little clipping. Then, right click on the main window, options-->preferences. Effects plugins-->Extra stereo. Enable @2.5, see if you like the way that sounds. That is my default. On the other, I like
but visit xmms for many other playlist plugins.
You can also try juk, a KDE app. I like it, but can't seem to get around not having extra stereo enabled.