And that is according to circumstance, but for the most part, it still holds true. In a typical system the subwoofer and tower speakers get driven the hardest and you want to do your best to distribute the load for better thermal performance. The power supply of an amplifier is usually the limiting factor when it comes to power, particularly when all channels are driven simultaniously. So you don't want to place an inordinant load or unbalanced load on one component. And part of it is that if I have a multi-channel amplifier sharing a single power supply, I don't like to run the lowest allowable impedance across the board. The set-up of the Supra OEM Kenwood Excelon systems made every configuration mistake possible and shut down often, although it wasn't bad equipment, just bad execution, and it was correctable.