Exactly, though depending on the sub(s) and box you may well see double your nominal impedance from 30-70hz, I have personally seen close to this. I suspect if he means that much clamped power he's talking about say a 10K amp per coil.
Where it really comes into play is 50hz and up where you run into thermal limits way before mechanical, particularly in larger drivers. Ever see a guy burping 160's in mid 60hz range?

