I've got a jeep wrangler and I stll rip stuff at VBR that tends to average 190-210 kbps.

Since I use a rio receiver and my computer to listen to tunes, the CD's are never used once they are encoded. Plus, should something happen to the CD's, I would have a method of recreating a new CD that is almost sonically identical to the original.

I can tell a 128 kbps in easily half the tunes I listen to. If I'm re-encoding for my workout mp3 player, I put in high and low pass filters (ear buds are pretty limited in what they can reproduce) and use an agressive VBR scheme to try and get a decent amount of quality tunes into my 64 megs.

It doesn't use any extra processor power to playback a VBR file over a CBR one, so I don't see the point in NOT letting the encoder decide where more bits are needed.