Miscanthus,
My 2 cents, if you want the cleanest picture possible, run video from Cable box to TV and don't go to anything in-between if possible. Higher the connection points the higher the possibility of interference. If your doing it to get the OSD, run a line from the 990 to the TV using s-Video or something like that, and do a Picutre in Picture to see it.
I have not read all the thread and so you might have a good reason. I'm a nut and I want the best picture possible.
Good Luck...!