Your in luck I have the same case and mobo. I was scratching my head and reading that one a few times as well. I decided to wing it and this is what I came up with. Speaker output works but. Don't know about the mic yet as I have not tested it. But if it is wrong you only need to switch the two mic wires.
from the asus manual----> case pin
bline_out_L ----> Return L (yellow wire)
Line out_L ----> EAR L (green wire)
NC ---> open
Bline_out_R ---->Return R (white Wire)
Line out_R ----> EAR R (red wire)
+5VA ---> open (nothing)
micpwr ---> mic vcc (white wire)
AGND ----> Ground (black wire)
mic2 -----> mic in (red wire)
good luck they are a pain in the @** to get in. I used tweezers.