I've got a 10gb mStation. A discontinued product from Traxdata.
Its Ok, not staggering but sufficient to compete with card noise and traffic noise.
When stationary you can here the difference from CD.
I recorded at 128k and have 2,500 tracks on it. You should achieve 5000 at that quality.
However, my head unit already has a cd autochanger (in the boot) and a satnav plugged into it and there were no phono connecters to plug the unit into the back of he head unit.
I ended up using the (supplied) RF unit. you tune a FM station into it rahter than direct connectiojn. this is why i used 128k - not much use using higher on FM.
some tracks sound excellent some absoultly unlistenable. I suspect its a combination of the encoding of the MP3 file - although it sounds fine thru my sound card) and an inferior mp3 decoder in the unit.
I suspect a direct connection and higher recording quality would yiled much better results.
Having winged I'm still happy with it.