Asked and answered all by yourself.
You could use the USB for recording and your soundcard for playback though but if you're going to buy a soundcard then why not a large diaphragm condenser to plug into it?
I use my USB mic for Skype and that's about it.
Here's a link for you, before you buy anything.
http://www.tweakheadz.com/guide.htm
It's light reading and very informative.
Have fun with it.
i need it to record rap vocals, i mean i want the recording to sound right and nice
I Skype my mother with that mic!!USB mics are universally slightly above complete excrement