Hi
It really does depend on how you listen to Music, if you just want noise, then yes 128kbs is adequate, but forget any bass or detail....
I use an extra small 4gb HP flash drive (
http://www.play.com/P...366693/-/Product.html ) in my car, which is fairly quiet inside, and a pretty standard sony head unit and a couple of 6x9 rear speakers, I would never even think about 128kbs, the absolute minimum for any decent sound would be 192kbs....
To be honest, 4,8,16 GB drives are so cheap now, that I actually use 320kbs and still have vast amounts of space left with excellent quality, to do this when ripping if you are using Windows xp with Media player 11, select under the RIP tab these settings: Format= MP3 and Bit Rate= 320 (best quality)
You really cant go wrong with those settings, however if you find that you are running out of space, just go down a setting on the Bit Rate, but seriously do not use anything less than 192 if you want to actually listen to music not a drone !
Hope that helps...