Getting audio from my xbox 360 to my PC speakers. Help

I want to be able to get the audio from my xbox 360 onto the 5.1 speakers my PC use. But on the subwoofer there is no connectors for the red and white audio cables xbox 360 use.

One solution I figured would get to get a cable going to the line in on my soundcard that would allow both the red and white cables to be plugged into it. Like a cable that splits into the 2 connectors for red and white. Would I lose any sound quality this way? And would I be able to use the full 5.1 surround setup I have?

I am willing to spend money on a new soundcard and speakers that would allow input from the xbox 360. Can anyone recommend a decent surround sound system for doing so?

Thanks

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