What is your soundcard now?
I would actually not get a new soundcard first if my card is decent.
I'll spend more money on the mic and preamp.Does more than getting a better soundcard.
Get a condensor like the Rode NT1, Behringer B-5, AKG C3000B, AKG C1000s, etc...
My preamp i would go for a M-audio DMP3 or the Audio Buddy.
If you want a mixer a Behringer might do the job but i would try the Soundcraft Compact 4.Not too far off from the Behringers but the quality is much much higher.
Don't forget your software like Adobe Audition or Cakewalk Home Studio or Sonar.The plug-ins will help alot.
How are you going to record?All at once?or one by one?