For in car usage Lame VBR 112k base rate is fine, at least in my Impreza, as the road and wind noise rule out being able to tell the difference. I did have everything on 128k CBR and it just barfed on Pantera tracks, and for a short while I went over the top to 320k CBR but ran out of space - admittedly the bit rate increases massively during some passages and one track comes out similar in size to a 320k CBR version!! The wonders of wide spectrum guitar widdling!
12Gb is just way too small - on 112k VBR I can get half my collection on it. Must upgrade...soon! Glad I've got a copy of Tony's drive upgrade FAQ.