well, what i do to stream to my LINE-IN, is just go to the SHOUTcast plug-in preferences, check "enable advanced recording mode" and then just instead of clicking PUSH TO TALK in the SHOUTcast plug-in window, i just LOCK it so i can do whatever. but then billions of people can hear every little burp or fart (if you're using a mic).
these settings are in the winamp preferences and in the DSP/Plugin effect window - just highlight SHOUTcast plugin and click "configure" button. hope this works for you - it works for me.
sorry bout the long explanation. i hate reading long posts, makes me an ass to post one myself