You should ask yourself where this is going for you,that will greatly help you decide waht you ned to purchase.
by that i mean- willyou continue to want to try toget better recordings, or will you be more contrained by budget to settle everything for a few hundred bucks and never look back. Or maybe getting into too much technical stuff may be distracting for you.
Either way, i am going to assume you are going to want to do a bit more than JUST record the piano. For a small investment youcan do pretty well. I will tell youthe stuff i bought, mostly from browsing these boards and reading reccomendations from otherwho own the stuff:
preamp/phantom power: M-audio DMP3, someone just sold one for $100 used in the free ads forum of this board, a pretty good price. This is a dual channel, so will let you record two small or large diameter condensors for a nice stereo image.
Recording software - Audacity will work, but you might want to look into other options with more functionality. GEt used to your equipment first though, it will help inform your decisition.
interface- not a bad idea to step aware from your stock sound card and its lame inputs, you can get a decent 20 bit card/interface for < $100 these days, especially used with everyone unloading their old stuff as they upgrade. You can get a very decent recording from 20 bit once you learn the basics.
Mics- lots of choices, i have 2 MXL 603s Small diameter condensors i would probabaly use for this, you can find 2 of these for $120-150 these days. Or plenty of people talk about using two SP B1s, but i don't own one yet, so nothing substantial to go on there. The good thing about a LDC like the B1 is that it can work on many vocals as well.
that would be enough to get you started and keep you going for a while. I bought the preamp, the 603s used, some monitors, and a few other items. I generally try to watch the free ads here and if someone has a good rep (good guys thread, etc) I will trust the purchase.
Daav