Line-In to Board Listen on USB Headset

[burgechris]

I have a Logitech USB Headset. I successfully listen to my music on my USB Headset and play my wife's music via my on-board sound system (ASUS M2N32-SLI Deluxe). For the most part, that rocks. I do have one issue right now where I have a line-in going into my on-board sound but I want to listen to it on my USB Headset. Also, I would like to turn-off and turn-on the ability of listening to the line-in (sound source is a TV stream) without having to unplug the line-in.

Clear as mud?

Thanks,
Chris