thats thermal power handling...... mechanical power handling you don't need more than about 400 watts for the 2 depending on the box
thermal means at the point in which the coils begin to have damage from heat
mechanical means when the cones pops out the box
adire says 650 watts thermal they won't handle that kind of power but in very small sealed enclosures ( or the correct ported one) and then all you get is a sub no louder than if you put 400 watts on them that is now very hot