There would be no way to separate the line coming in. You would have to bring them in on their own separate channel. Then you would need software / hardware that would route each channel to a specific speaker. If you're hoping to do this with standard 5/4.1 computer speakers this isn't going to work unless you find some software to route the channels and even then I don't think it would be possible. The very minimum you would have to separate the output from the 4 wows on 1 machine.
I think the best you're going to do (cheaply) is just run your 4 wow's to your line in.
This is where running multiple PCs has its advantage. I run 4 PCs sound outputs into my mixer and I can mute / unmute just by turning the volume knob.
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