To answer your question, yes you can have two sound cards. It's not recommended but possible. There's a lot of problems that could be caused having two or more sound cards installed at once. Not many applications like this and it can cause an IRQ problem.
You might want to think about looking into some usb headphones. Plug you speakers into your sound out jack from your sound card. And plug in some usb head phones into an open usb port. Then its a matter of configuring your applications to use what device you want.