It is very hard if not impossible to tell someone else what the “best” MP3 encoding settings are for them. MP3 encoding is all about striking a balance between what sounds good to your ear and what size MP3 files you are willing to live with. And, to a certain extent, your minimally acceptable bit rate will depend on the type of music you are encoding (i.e., rock, classical, jazz, country, etc.).
Try experimenting by selecting a representative song from your collection – one that has a wide range both from a frequency standpoint (parts w/ a lot of bass, and others with a lot of treble), as well as from a volume & complexity standpoint. Then, using that song, experiment with different settings, naming each MP3 file different names so that you can perform side-by-side listening comparisons on your iPod. Then, pick the one that sounds best to you with the largest file size that you can live with.
Having said that, many people would recommend VBR, especially if you are wanting to rip & encode at lower bit rates (say, less that 256 Kbps). And, some people think MP3s sound better encoded using normal stereo instead of joint stereo.
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