It's usually not the speakers fault. It's usually them clipping the input signal to the amplifier that's causing the speakers to blow. Square waves in an audio signal is NO GOOD!

Most of the time, a speaker should have 3 times the rated amplifier power. I've very rarely heard about a speaker blowing from too MUCH power. You really need to calculate how loud you want the sound level to be at the distance they are really using it and pick the speaker that is efficient enough, or has enough power handeling to deliver that kind of level that distance. If you want more info on these calculations, just give me an email. It's fairly basic really.