Most of the non-DTA Comcast remotes (the silver and grey models) are JP1.x remotes. You should see a 6-pin header in the battery compartment. There is a cable and software you can use to create and add your own devices to the remote.
I would however just like to use the power and volume control for the Sony box most of the time. When I am using the Blueray and sound system adjustments, I agree the Sony control unit is the best idea. Any codes for the Sony unit?
most codes for devices are for on off only the comcast remote is limited in this manner it is not a true universal remote. You are better off just using the remote that came with the system. you arr probably also going to find if the instructions tell you to put all the hdmi inputs through the receiver and back to the tv that the comcast box will not play nice in that set up. so if that happens use an optical audio cable from the box to the receiver and then go hdmi from box to tv.
Purchased a new Sony Blueray Surround Sound system, model BDV-N790W. I have used every code for Sony in the areas of audio and DVD/Players and I have not found any of them to work on this unit. Should I be using a combination unit rather then and audio or DVD player?