I just wanted to post this in case it helps anybody. Maybe it should be posted somewhere else as well.
I hooked up my 650 with analog cables because that's all I had, luckily I had an adaptor so it went from one jack and split into the red/white to plug into my receiver. It's an old receiver without hdmi. I liked that I could choose variable output and only had to use one remote to control the volume, the cable box remote controlled it thru the tv.
My optical audio cable came today. I don't even know if it's a better way to do audio or not, but I got it cheap. I couldn't get it to do variable output when hooked to the tv, so I hooked it to the cable box. Still not variable, the cable box did not control the volume. Many webpages told me I can only get fixed audio with optical. Well, that stinks. I have too many people who can't handle using a separate remote for volume, or can't grasp choosing the device button on Comcast remote to switch between receiver for volume and back to cable for channel. It often messed me up to because if I started to enter a channel while it was set to receiver, it would change the input setting on the receiver! . I found this page on Comcast forums which explains how to LOCK the volume key on the remote to ONE device. I set it so that the volume button always controls the receiver only and I don't have to switch using the device key. My optical audio is now variable! http://forums.comcast.com/t5/XfinityTV-and-Equipment/Control-audio-on-cable-box-instead-of-TV/td-p/1115959
I currently have the optical cable going from the cable box to the receiver. I'm not sure where the DVD is hooked to, but we don't use it much. It's not hdmi either...it's component.
Should I move the optical cable back so it goes from TV to receiver? Then hook the red/white from the dvd also to the tv? Will that work? Or I could just hook red/white to the receiver from the DVD.
I just had a thought as I typed, I guess I will try the optical back on the TV again, otherwise I won't have sound from the apps......
Had TV since a week before Thanksgiving. Still working well. My mom had the E601, after about a month half of her screen dimmed. She returned it and got a Samsung.