There doesn't really need to be any connection between the two. Any video source can be connected to the scaler, but I'll have to let others with scalers comment on how much difference they can make (and how to best configure the video sources - I suspect it'd be best to minimize the amount of video "tinkering" the DirecTV or cable box does so that the scaler can do all the real work). The macros themselves should be very simple - instead of sending the signal to the 990 asking it to switch to the "video2" or "DVD" input, you simply send that command along with a command to the scaler to switch to the corresponding video input.