They're more resilient than you may think ;) I think that one died as the result of 4kW being applied to it...
With the cabin gain at low frequencies found in most cars, the low end extension of even little 1-cubic foot boxes is pretty impressive. But my favorites were the ones where the entire trunk was sealed off from the cabin to maximize airspace - as long as the woofer stayed together, you could get honest-to-goodness infrasound out of the thing...