Mazda and Kenwood had it right. When an amplifier is bridged, the combined mono channel "sees" 1/2 of whatever the impedance it's being presented with. In our case, the amp sees a 4 ohm load with the 8 ohm sub hooked to it...which is a safe load and won't get the amp running too hot. As for the 14.4v rating, we should get about that with the engine running. I personally don't care for amplifier manufacturers using the 14.4v rating. I prefer amps that are underrated and are spec'd for 12 volts. For instance, my Autotek 99 sub amp- It's rated at 99 watts, but is capable of 10 times that, even in stock form. Mine in particular was souped up from the factory for the guy I bought it from. He was sponsored by Autotek and Savard back in the day. In his truck, I saw this amplifier pull 105 amps of current according to an inductive meter. 105 amps x a running voltage of, say, 13.8 volts = 1,449 watts. It's a beast, and it's only limited by your ability to feed it enough current and keep it cool. This amp drove 8 12" Savard subs and produced 163 db. The one time I attempted to sit in the cab of his truck for 5 seconds I jumped out and threw up all over our installation bay!
Of course, our amp should be capable of 2 ohm stereo/4 ohm mono loads. I don't know. Like I said, I'm just beginning to start work with the stereo in my MSP and haven't dug into it fully yet. The whole project just accelerated when the original head unit got thugged this weekend.
Right now it's getting the window replaced. First things first.
