Why would they build a Tivo that doesn't tune in local stations?

because in a DirecTivo, there is no need for an MPEG encoder chip. the MPEG streams are stored directly as received from the dish, so a whole chunk of circuitry from the SA models can be tossed out (along with the cost).

that has always been the harsh tradeoff between an SA and DirecTivo: do you go for the dual tuners and (potentially) higher video quality of the DirecTivo, or go with the SA that can only record one stream, but it can be from any analog video source. some people end up with both boxes.

--dan.