Here is a piece of software that I am not able to test myself as I run Linux but maybe we have some folks that might want to give it a test run. It accesses your sound cards many features, including beta versions and allows you to decide exactly what your sound card controls. Line Input, Stereo Mix, etc.
Read more or download it here. LINK
So what is the point of multiple sound cards?
You can have multiple apps each with separate input/output ports.
For instance, during The ALPB TeamSpeak meeting I'm using one soundcard for the TeamSpeak meeting while my other sound card takes care of the audio input/output for my FM yardcaster.
I use the main sound card to preview tracks and the second to transmit my station to the FM transmitter.
