I learned some of the codes from the OEM remote today using the IR Pro, and they worked when I tested with them from a T4x. I sent them to my buddy to see if he can generate the discrete inputs for me using that information and some additional data from Sennheiser.

Sadly, Sennheiser confirmed that there are no discrete power codes. Their engineers are fresh out of college and haven't lived in the real world. We'll have to wait for them to grow up.

I am going to see if the USB port on the soundbar can be used to sense its power state. I'll feed it to a sense port on the XP processor if it does. That way I can manage power of the device, and use the discrete input commands to select the source I want.