Several things to keep in mind:
1) Your soundcard is decent, but not great. Don't expect a flawless, pristine recording out of an audigy.
2) Pianos generally sound best recorded in stereo; you can't do that with just one mic. Also, I don't believe the audigy has any stereo input, but I could be wrong.
3) Do you have a preamp? A mixer? You'll need one or both to plug the mic in and supply phantom power.
I definitely think the NT1A is an excellent choice of mic. I have two that I recently got for recording acoustic guitar, and they sound absolutely fantastic. I don't know if they'd work as well for a piano, but they are absolutely perfect for recording acoustic guitars.
As for preamp/mixer/soundcard, I'm sure there are products out there that could cover all three; look for audio interfaces with decent mic preamps and phantom power.