If you want to stream with live, and your sound card, does not allow What-U-Hear, or Stereo Mix, as it is also called. You can use this program, called Virtual Audio Cable, which will give you a digital "What-U-Hear" component. This way, when you record live, you can stream the in-game sounds to the viewers.
I'm referring to this guide, for setting up the broadcaster:
http://mmorpgforum.net/showthread.php?t=184645#nine
And here is a link to the Program (Virtual Audio Cable):
http://software.muzychenko.net/eng/vac.html
Good luck and have fun with the Broadcasting!
P.S. If you have any issues with this app, please just post here and I'll make a more detailed guide, but for now, I don't think it's needed.