As to expecting "more bass" because of the extra driver, as Casey pointed out, an extra driver generally results in having a greater power handling capacity and can therefore play more loudly at a given frequency within its range. There wouldn't necessarily be any lower bass extension, and the Axiom spec is in fact identical for the M100 and M80.
As to power requirements, "reason" can't be applied. Often the larger speakers in a given manufacturer's range of speakers are slightly more efficient than the smaller speakers and therefore require less, not more power. This is the case with the 1100/880/660 range, as the Axiom spec shows the 1100 to have a 2dB higher sensitivity than the 660 and 1dB more than the 880.
