I met Dave, the electrician's A/V expert, at one of their other jobs to look at how their systems are wired up and configured. They had structured wiring throughout their house, wired back to a centralized A/V room. The A/V room will eventually house their media server and Xbox 360's for streaming video from the server to each zone. Each zone is also wired up with in-wall speakers, and all the wires go back to their A/V room.
We'll probably put the Xbox's in each of the zones, instead of in the A/V room. The Xbox's will run Media Center and stream video from the server. The TV's will be connected to the Xbox's with HDMI cables. And the line level audio from the XBox's will go back to the A/V room where they'll be switched and amplified back to the speakers in each zone.
Their house was wired for touch panels, but we'll probably use wireless devices instead of fixed panels in the walls.
I still need to get a better grasp of how the security system and lighting control system will be tied into the A/V control system...