If you know your way around linux a little and dont mind spending a bit of time setting it up you could have a look at LinuxMCE as a possibility (I'm just waiting for my download to complete so I can have a play,considering moving from Media Center to this to get HD playback for Freeview).
Not sure if it would work out cheaper or not as you would need to purchase a high end PC to put it on and some form of reciever in each room.
By central hub, I am assuming you are referring to a central wiring hub.
I would point out that yes you can distribute this media around your home through a central hub. The central hub systems usually use a RF modulator to distribute the signals.
However, the content will not be HD it will be in SD (standard definition). As long as this meets your future requirements then all is fine.
To achieve HD distribution is a different ball game and currently adds $$$ to the cost.
1 Touch Automation.