Well, I broke down and got a second sound card, installed and got it running no problem, but Shoutcast has been having issues deciding which card to use (this is an informational post - not a question, just so you know.)
If you want to run a call in show, I have found that you will need at least 2 separate mic inputs - the SB Audigy does this on it's own, but for older sound cards, you will probably have to install 2. Once both cards are installed, open the properties dialog in Winamp and go to the Output section. Select one card to use in the list here.
Second step is configuring MSN. Go to Tools - Audio Tuning Wizard and follow the steps, selecting the SECOND card when asked.
That's it

Now I just have to figure out how to get the voice chat running through my firewall