Nah, if the DACs on your sound card and all your wiring are high quality, analog sounds as good as digital. In fact, if the DACs on your sound card are better than the DACs in your speaker system (when using the digital input), the analog setup will beat out the digital!
That being said, I would definitely go with a sound card with 18-bit or 24-bit DACs. I think the Live! had 16-bit DACs and they are noticeably inferior to the Audigy. What does the GTXP have, 18-bit?
Ritesh