Julian if you still want to get your mic + comp sound working, you can probably do it using Virtual Audio Cable (but you'd have to find a full version of it). Basically turn on a virtual audio cable in the program, then open two copies of their Audio Repeater (comes with it), have them repeat Stereo Mix and your Mic input -> the Virtual Audio Cable, and then use the cable as your line input on the streaming program. Basically it mixes Stereo Mix + Mic together.