re: Firefly theme
I don't have Serenity on disc -- yet -- but I have a decent memory for music, and the Firefly series on DVD. The series theme, "You Can't Take the Sky from Me," is a song. As I recall, the film did not use the series theme until the very last of the closing credits, and then only as an instrumental. AFAIC, the Firefly lyrics are a lot more meaningful (and applicable to the story) than Enterprise's were.
For the record: I'll take the DS9 opening theme (the re-mix from the later seasons) over all the other ST series.