For
C Band you really need at least a 8.5' dish. For Ku you really need a solid dish. So as we look at this a solid dish 8.5' or larger would cover your needs. Now you can go with either a traditional feedhorn and 2 lnbs (1 C and 1 Ku). With this you will need a receiver designed for a big dish to control the skew of the lnbs and movement of the dish
OR
There is a C/Ku lnbf on the market now that could be mounted to the dish that woudl also fit the bill of strictly receivers of the type sold at
Sadoun's. This unit will not work with a 4DTV receiver where the above will. Advantage is cost (low for this unit compared to the above configuration) Disadvantage would be not being able to use it with a 4DTV receiver should you decide to add one in the future.
If you went traditional you would require a
DiSeqC switch to change between C and Ku (receiver does this automatically) with the lnbf it is built in. With the lnbf you would need a
VBox to move the dish. It converts DiSeqC commands to 36v for the
actuator.
Other iten of thought. With the lnbf you would only have a single coax cable coming into the house. With the traditional feedhorn configuration you would have a large ribbon cable.
Hope that helps a bit