Due to how this game is designed, these things could easily double the required size of the whole game, making it twice as long to download. I don't see it as a fair trade.
I love the music in this game, however I will admit more sound could really bring it up a notch and make it more immersive, but the story lines and game-play for me are what make this game so unique among it's peers. That being said, I wouldn't mind leaving it downloading overnight if that's the trade off, it would bring back memories of times passed. But your game is already 20/10 for me regardless ;)