I must be missing something but I thought the overwhelming majority of wattage is being delivered on the 12V lines which these units do not touch, especially because most of the 12V pins are in the 4 and 8 pin connectors and not the 24 pin ATX connector. Even the beefiest PSU doesn't have more than 120W on 3.3V and 5V and I bet most of that is intended for spinning rust disk usage and not for the motherboard. So ... why do we have 80W, 120W, 160W, 400W units...? What's the difference?