Ian,
I think it might be easier to consider what max voltage is needed at each speaker section rather than power..

There are two parts to consider: the driver section needs (voltage/SPL/freq) and the max content peak voltage over frequency relative to a reference (say 1kHz). The driver part you have and I’ll bet that the content part has to be known if you don’t know it already ... ( if not, it would not be a hard reasearch project given all the online content. Know of any a grad students who might need a topic?)

Armed with this info we can talk about relative amp clipping and power.