I've got a 2 channel amp. It says the suitable impednece for stereo is 2-8 ohms, and the suitable impedence for a the amp (as a bridged amplifier) is only 4-8ohms. I know that when you double the ohms it cuts the power by half, but I don't understand why it would not allow two 4 ohm subs to be bridged, sense it would allow one 2 ohm sub to be connected. Someone please explain this to me. Thank you