How can I replace the Comcast rental cable TV box with a DVDR that includes the secret Comcast decoder ring?

I don’t want to pay for that box every month, year after year. In a few years, that scruffy little box will cost me more than a state-of-the-art entertainment center, and I’ll keep right on paying for it year after year as long as I live on a Comcast feed. I want to break free of that curse. But how? What do I need to buy to receive all the standard, premium and on demand channels without paying Comcast for a box to decode the signals?