1) 20GB should be sufficient to fit 7000 to 8000 titles.

2) the music quality on all Creative products is without peer. The cost is terrific for their items.

3) They will support all music types except, of course, those from Apple. They are usually also compatible with all music store sites.

Their included software or WMP10 will allow you to add a song(s) to any library that you wish.

Many vendors supply cassette to device functionality for your vehicle. See nomadworld.com for other assistance.