You have to have the HR20 to get the new local HD channels correct? I have a Tivo HR10-250 and 3 LNB dish.
All new HD is MPEG4 and on the KA sats. This is now the HD locals but next year will be all HD from DirecTV. Thus your old HR10 cannot receive them (and never will).
You need either an H20 or HR20 (HD-DVR) and the new 5 LNB dish.