I have read a lot of posts about different TV tuners. What I am looking for is an external tuner that I can plug my cable box into and be able to record all HD channels (including HBO HD, Cinemax HD, etc.) Which tuner will be good for this? A lot of posts are saying that those channels are "encrypted" but I believe if I use the cable box instead of over-the-air that I can record any of the channels that I receive. Can someone please advise me on this? Thanks