I created a model to figure this out, based on your estimate of 200 songs.
8gb: 200 songs, 1 full length divx movie, 5 video clips, 500 pictures and 50 apps
16gb: 200 songs, 1 full length divx movie, 5 video clips, 1250 pictures and 50 apps
a full length divx movie is about 80 pictures and a video clip is about 10 pictures.
Hope this helps!

