Connect them all with BNC "T" connectors Digi as master then Apogee AD-16X and DA-16X then the rest.
This setup allows you to control wordclock from inside PT and yet still get the benefits of "Big Ben" which are inside of the AD-16X and DA-16X. (Also the manual for the X-HD Card says that any DIgi boxes need to be first.)
The Apogee website is actually a good resource this kind of stuff; look under "Support."
Nick
