Jimmyj,
That method is not going to work because all that header does is bring your front panel HD audio connections to a header on the back of the case. You still have the problem of having one sound card that cannot handle 2 separate outputs.
The easiest way around this is to get a simple USB to coax or digital adapter, this can act as a second sound card and can be setup to get output from winamp or the like. Here's a larger example of what I'm talking about but you should be able to find one for cheap, they're pretty common for laptops that don't have digital outputs on them:
http://www.amazon.com/gp/product/B00..._cp_ob_title_0
Hope that helps you out.