Are you using the Realtek drivers and applet? When you plug a speaker or mic in, a window should pop up asking you what it is, and if it's a speaker, give you the option of choosing its location in a multi-speaker setup. If you're using SPDIF to you amplifier, you may have a wired, optical or both connectors on the back panel. It's (usually) a plug'n'go solution. The driver package can be downloaded from Realtek, and is more recent than the W7-supplied driver.