I would opt for the full HD cable box or a Roku. I can't see the point of having a 55" HDTV and feeding it standard definition signals. There is more to a full HD signal than the loss of black bars. Even a 720I picture is visually better than a standard definition 480I picture.

I dropped cable. I use an antenna for over the air TV. All the networks broadcast an HD picture over the air. To replace cable I bought a Roku and subscribed to Netflix. In addition the output from the Roku box is HD. At $8 a month it's one of the best buys I can think of.