My cable box (Comcast SA8300HD) is going right to the 990. It's either optical or coax, don't remember off the top of my head.
Funny that you mention the balanced cables - I'm using balanced on the front 3 channels but unbalanced in the rear. This 'pop' is annoying, but it's not worth buying 3 new cables at this point.
Anyone running balanced cables and not experiencing any pop?
Cheers
Edit: I suppose the easy thing to do to test this would be to swap out the balanced cables in the front with the unbalanced cables in the rear...just a matter of me wanting to go back in that zoo of wires that I have.