reply to jonb
Re: Basic service sub required to recv other levels? Depends if the "letterboxed" (SD) channels on YOUR system, are also offered in an HD feed to begin with.
If those said channels ARE offered in HD, then adding HD (tech fee) & swapping to an HD box should fix it.
Most HD boxes have HDMI, component, composite AND RF (coax) outputs, so they can work on ANY TV; you can find out when you go to swap boxes at your local service center.
If those channels do NOT have an HD feed on YOUR system, adding the HD fee/box isn't really going to help much, until CC adds the actual HD feed to work with your HDTV.