You have to change your headphone output from all audio to chat only. At the moment you are getting sound down the USB port as well as optical. You are getting the 2.0 stereo along with chat from the usb as well as the 5.1 over optical. And no, 2.0 stereo and 5.1 Dolby does not add up to 7.1. The mixamp/ base station unmixes the 5.1 to 7.1 already. If you like the sound you getting from both inputs simultaneously, then there is nothing wrong with it.