On your current design, does it have regulated 12v now? If so, what is the power output on that?
I'm in the planning stages of a carpc setup in my 18-wheeler. I would only need the switched power for the lcd monitor in the sleeper of the truck.
The regulated 5v is perfect for the usb hub. I have 2 in the truck (currently running off a laptop). I have one powered and one unpowered and it's all working great with that setup.
The main thing I'm wanting to do is to get rid of all of my power inverters (I have 2 - 1 75watt and 1 400watt).