When you say the Panny has an Optical out are you saying you use the Panny to feed the audio stream to the 990? You should be able to run the video HDMI out on your Directv box right to the HDMI input to the TV and the Coaxial audio output of the Directv box to the 990 coaxial digital input (it is orange colored RCA connection and is not threaded). My Directv boxes do not have a coaxial audio output but they do have HDMI and Optical.

Configure the 990 so that the audio from the TV box is the default when the TV is the video and it should sound fabulous. You can also use the digital optical out on the TV box to feed the 990.