If you used the Enter key to send your post, that means that users would have to find another method to force a linefeed when they wanted to divide their posts into paragraphs or lists.
I'm not sure having sounds would be a good idea, and having them could quickly become very annoying.
Example: When you open a thread, if more than one post has sounds attached, you could end up with too many sounds coming at you at once, which would defeat their intended effect.