Ravi, the point is that each section of the speaker would be driven by a 70 watt amp, not a 140 watt one. A recent generally excellent review of the 3805 for some reason used the figure of 240 watts if bi-amped, at least implying that that power would be available(some posters on other boards have taken it to mean that). In nearly all receivers the power supply section is the limiting factor in the amount of amperage that can be supplied and dividing the amplifier sections driving a speaker into two doesn't increase the capacity of the power supply section.
