Looks good. It should be noted that if you use a powersupply such as the OPUS, you'll have a main cable going to the battery, a wire to the ignition, and the contacter would be replaced with the wire from the OPUS.
It's also important to note the IDE>USB adapter. Even though you are using a USB2.0 hub, when you put 1.1 devices on the hub, it causes all the devices attached to it to run at USB1.1 speeds. This may not be perferable since USB1.1 operates at 12MB/s while USB2.0 operates at 480MB/s. Recommend, in this case, that it gets its own USB cable going to the motherboard.
Also, if popping noises are heard for the speakers during powerup, the use of some sort of delay timer or circuit may be needed. Search the board for options (I've posted in some of them.)
Attached is my propsed wiring that I plan on using. (You'll see that my DVD and touchscreen are on the same hub. This is a mistake during drawing and I just have not taken the time to change it.)
View my Worklog to see some of my progress.
Downgraded Progress - Starting with another car... 09/13/06