Dear Paul,
find comments below:
1) yes
2) partially: you can add a Youtube video to each song
3) catalog sorted by genre coming on version 2.0 (to be released on February probably. Free upgrade)
4) search feature for audio. Music Collection is oriented to audio, not to video. video is only an add-on
5) don't know exactly what you mean.... Admins can set up if the files can be downloaded by everybody, registered users or nobody. uploads by client coming on v2.0
6) link for external ecommerce feature. NO paypal integration in music collection. "ecommerce" feature included in Music Collection, with paypal transactions, coming SOME TIME in 2010. yes, I know that's not very specific information...

I just can tell you that once version 2 is out, we'll start working on a e-commerce edition
7)yes
8) don't know exactly what you mean... but no
all the missing features you want can be programmed customly, but the more delicated point is #6. this is a serious thing, and it is A LOT of work (A.K.A, a lot of money

) if you want the ecommerce feature integrated into Music Collection
to make a quote on the videos feature we'd have to specify all the exact features you'd like (how you'd like to present the videos, etc)
best,
Germi