Clay, the point is just that the speaker(including its impedance, since nothing analogous to that imaginary center tap is happening)doesn't change; it's the amplifier that changes. Of course if the added maximum power capability present when bridging is actually used(unlikely), then more current is necessary for the increased power, but it's because of the increased voltage from the amplifier, not any decrease in effective "seen" impedance in the speaker. If the use of the "sees" terminology is necessary(shouldn't be), then maybe it should be said that the speaker sees twice the voltage.
