For the best balance between quality and space when ripping CDs, I usually use VBR between 192 and 256 kbps (of course, make sure to use LAME.) I can barely tell the difference between that and CD quality sound, and only in the bass at that. With that, you can fit about 10 hours of music on a 1 "Gigabyte" mp3 player. However, unless you really demand the utmost quality to your sound, ripping at 192 kbps or VBR between that and a lesser amount should be just fine as well. 160 by itself is a bit low and 128 should be out of the question if you have any decent headphones at all.