Ok, I too wanted to know this, so I looked arround a little and after a little while, found out whcih header was which. The hedders are on the top left of the card, and starting next to the SB logo are:
1. analog ground
2. analog headphones out L
3. backpannel mute (mutes the speaker outputs when headphones are connected)
4.alanog headphones out R
5. backpannel mute again
6. microphone input
7. don't know (but not important...I don't think)
8. voltage referance for mic
9. mic input muten (will be ground if no mic present, 12v if mic is present)
10. audio cable detection (goes to ground if headphones are plugged in)
I haven't actually tried these because I havent got a audigy2 yet. But it should work!