You don't need all that. Plus the adapter in the form of a cord wouldn't get you sound out of all speakers.
Just get the Stereo Y-Adapter. You can find it at Radio Shack in a Gray/pink packaging. Plug the red and white plugs from the console to the respective slots in the adapter. From there, plug the adapter into your sound card's line in connector. You may have some trouble pluggin the microphone and the adapter in at the same time because the adapter itself is so thick, so get the 1/8" headphone extention cord and plug the adapter into one end of the cord and plug the cord into the sound card.
I'm not sure how much the extention cord is, I found it at school. The adapter is about 4-5 bucks.
If you're not getting any sound from the rear speakers, search this board for getting cd-audio from all four speakers. Follow those steps and if you're still not getting rear sound, you may have the wrong adapter. You can easily exchange the adapter from radio shack for a different one, refund whatever... Tell me what happened.