Alrighty, I've run into a couple of minor issues.
I've got an SPDT power switch hooked up to the M2-ATX. The problems:
1) Weird behaviour: While I'm driving, I might decide to power down the system, so I press the power switch, and the PC hibernates and turns off. The LCD turns off. The fans stop spinning .... and then I hear them spinning up again and the LCD turns back on and the PC starts up again. I wait for it to start up fully, and then I press the power button again. It turns off, and stays off. It always happens like this. Is this normal behaviour? Perhaps it's an M2-ATX issue?
2) Not a major problem: I can turn the car PC on and off without the key being in the barrel. But if turn the PC on without the key in, the amp doesn't turn on. So am I correct in saying that the M2-ATX only turns on the amp when it receives the signal from the ACC or IGN circuit? Any workaround for this? This isn't a major problem for me because like most people, I usually have my key with me when I'm in my car, so I can simply put the key in and turn it and the amp will turn on with the car PC.