Also does anyone know what the duel stereo setting is for or if that would be better?

I don't know if dual stereo is the same as Joint Stereo, but here's the way stereo MP3 encoding works (if I understand it correctly, someone correct me if I'm wrong):

Most music shares a lot of information between the left and right stereo tracks. Many instruments are panned center, or only a little bit to one side or the other. Joint Stereo encoding tries to take advantage of this, by devoting bits to specify that sounds are on the left or the right side only when those bits are really needed. This lets you spend more bits on the whole music track, making it sound better overall for a given bit rate. The drawback is that sometimes there is a little bit of stereo separation sacrificed.

Pure stereo MP3 encoding treats the left and right channels as two completely separate audio streams and encodes them independently. This means you only get half the bits for the left channel and half the bits for the right channel. So a "pure stereo" MP3 file at 320kbps will have perfect stereo separation all the time, but each of the channels is only 160kbps worth of quality.

Most everyone encodes in Joint Stereo.

Anyone have any corrections to make to that? Have I got it completely wrong?