Good thread because I have been wondering the same. I am looking at Dish because of the dual tuner system. I have 5 TV's that need service with 2 of them that are HD. The other three TV's can run SD because they are rarely used. How do the dual tuner units work? I'm guessing that I need 2 HD dual tuner units and 1 SD dual tuner unit. How do you go about changing channels on the TV with no receiver and how are they hooked up together?