I would say YES! Of course your source material will figure into it, but the X-Fi and its software does a much better job with sound than the SBLive. Some of the biggest sound difference will come from stripping the hiss outta MP3's.
I play MIDI files alot and the 3D MIDI player and soundchip sound SOOOO much better on the X-Fi. The only thing I would tell you to consider is there are other soundcards out there that may be better at MP3/WAV type playback, but may sacrifice a bit in the gaming area. For me, the X-Fi is great for a mix of music and gaming. Now if Creative would only get their Vista act together...