Fred, note that the equations for bass extension make use of Fs and Qts, but not Xmax. The additional excursion represented by the 12mm Xmax affects the maximum sound level, as Ian mentioned, rather than the frequency of the extension.
John. I actually entered the t/s parameters into winisd and did some modelling. I know a model does not tell the whole story, but this new driver appears to be capable of more extension than it gets in the M100.
I see Ian's point about the value of that extra extension in the M80/M100, but I wonder what it might do in a bookshelf?