Neat article. I'm on the middle of page 2 and I disagree with the bottom bit about amps. Suppose the 12V line can put out 20A max (240W). The devices are connected in parallel so they get the same voltage and different currents... then the current delivered by the power supply is the sum of the currents through each of the devices. Note that this means the load is "too much" beyond 20A and beyond 240W (these will always occur at the same time -- you can check for either excessive wattage or amps and one implies the other).