You need to find the max size that your head unit will accept. For example, the new Pioneers can only handle 5000 songs in 400 folders. There was a guy at one of the car audio forums that found this limit by connecting a 60GB drive.
If you have an MP3/MP4 player that supports AMV video playback, then you will need the AMV Converter to convert videos to AMV file so it will be playable on your player. This version can now encode .AMV files at 128X128 resolution as well.