I guess Mr. P and I both thought of the same thing.
IMHO- I don't know what use it would be to me since most lightsters want to be the first on their block with a particular song sync'd. Not everyone though, I'm not in it for the competition, I'm in it for the fun.
I just cant see going/ joining another site just to get music ideas for syncing.
With lights esp. Halloween almost anything goes.
Also FYI MP3 millions is a lot more affordable for MP3's than the ones you mentioned. I've been using that site for years. I only go to another site if 1% chance they don't have the particular MP3 I am searching for.
That's just my opinion though so charge on.