I think you're right. Most places don't expain all the hardware requirements for HD when they buy system components. However, in the end, it's really not that complicated.
Most people make the mistake of getting an HD-ready TV, hook up their antenna, and can't figure out why there's no HD picture. In either situation, sat or cable, the box is the key. Even with cable HD, the HD box they give you may not take an antenna feed, and you may need a second external HD box for the off-air programming. Keep that in mind when asking your cable company about their HD service and components.
