I don't have time to read all the replies but I'll give my take on the subject.
You can blow a speaker just as easily by under powering it as you can by over powering it. When you under power a speaker, the amplifiers dampening factor looses control of the speaker and allows it to move out of control which in turn will create heat in the voice coils. A woofer with too much power will at least be under the control of the amp but be over driven past its limit of excursion. This can result in bottoming out the voice coil in which case the woofer is still trying to travel beyond its limit. This too will create a heating of the voice coil. Both can be prevented by the proper choice of equipment and correctly setting the gains. Another factor comes into play as well. Power & ground. While many people buy big power wire, they don't always upgrade the ground. In addition, many cars are glued together now. For example, a Ford f-150 can have as much 15 ohms of resistance from the metal behind the seat to the battery. This problem can cause the same effect as under powering a woofer. It can also cause amps to shut down. Especially on a regulated power supply. A regulated amp will try to produce its full rated power no matter what voltage is going into it. Problem is, as it runs out of voltage, it also looses dampening factor. Now you are in effect, under powering your woofer and it's now flying out of control and trying to burn itself up. If you are experiencing what seems to be an underpowered situation, I recommend checking the resistance of your ground location to the battery. Don't rely on scraping the paint. It won't matter if the vehicle is glued together. If there's any part of this I need to elaborate on, let me know. I hope this helps.
You can blow a speaker just as easily by under powering it as you can by over powering it. When you under power a speaker, the amplifiers dampening factor looses control of the speaker and allows it to move out of control which in turn will create heat in the voice coils. A woofer with too much power will at least be under the control of the amp but be over driven past its limit of excursion. This can result in bottoming out the voice coil in which case the woofer is still trying to travel beyond its limit. This too will create a heating of the voice coil. Both can be prevented by the proper choice of equipment and correctly setting the gains. Another factor comes into play as well. Power & ground. While many people buy big power wire, they don't always upgrade the ground. In addition, many cars are glued together now. For example, a Ford f-150 can have as much 15 ohms of resistance from the metal behind the seat to the battery. This problem can cause the same effect as under powering a woofer. It can also cause amps to shut down. Especially on a regulated power supply. A regulated amp will try to produce its full rated power no matter what voltage is going into it. Problem is, as it runs out of voltage, it also looses dampening factor. Now you are in effect, under powering your woofer and it's now flying out of control and trying to burn itself up. If you are experiencing what seems to be an underpowered situation, I recommend checking the resistance of your ground location to the battery. Don't rely on scraping the paint. It won't matter if the vehicle is glued together. If there's any part of this I need to elaborate on, let me know. I hope this helps.