Your totally correct. Impedance dips in the 100hz-300hz will stress amps especially at rock concert levels like we are seeing here. Frequencies at and below 100hz are the most demanding on the amp and can quickly put it into current limiting with the right material. It will add greater power demands and more heat generation running them large...it might not make any difference, it may make a difference or it just might take a little longer before they shut down raising the crossover point....
If you don't have a sub still try an 80hz crossover point and repeat the same conditions. Don't worry how it sounds. This is just a test to find out how the amps behave with the speakers when you change the settings.
