Any Audigy can put out analog audio quality that pushes what humans can perceive. In fact, unless the audio solution is noisy or really destroys the signal most people have a hard time telling the difference between solutions at all.
X-Fi will be a complete waste of money unless you play games that support it's special features AND use headphones. It really isn't going to be noticeable otherwise. Music would be equally well served by a cheap Envy24 board, or almost any board honestly. You just need good signal quality. Hardware acceleration does nothing for music.
Speaker quality is far more important than the audio card in most situations. Unless your audio card just sounds horrible.