Now this is a tough question to answer.
The sound on your motherboard is a little better than an Audigy 1 but with hardware decoding.
So.....
The Santa Cruz has a better..cleaner..and warmer sound than the Audigy 1 but the A1 has slightly better gaming support.
However, you will not have the glitchiness with the SC as you do with the Sound Storm. For those of you without this sound "option" it's not a really a glitch just the drivers could be a bit better. I did notice some noise with the Sound Storm myself. It's really a hard decision honestly. I would say it would come down to price. If it's cheap get it and/or if you have it already try installing it and see how it compares.
You should also might want to keep this thread in mind as far as drivers for the SC go.
New Turtle Beach Santa Cruz Drivers For All OS's