Only 1000 watts? Gee, last time I checked not too many speakers have a continous power rating of much more than that. DD's are not very good for home use, if you want them as a subwoofer. They have a high free air resonance, and were designed to be SPL drivers, for the car market where you get cabin gain.
As for the 5000 watt, where do you find that rating? I assume you are saying that is a continous power rating? If so, that is incorrect.
As for the 30kW rating, that is plain BS. Who told you that? Mechanically, you would have to play a VERY high frequency to prevent the driver from bottoming with that kind of power. I would imagine power compression would come into play A LONG TIME before that. The only time the driver could handle that kind of power would be for SECONDS, if that. Also, what kind of amplifier did they use to power it? Last time I checked even for a DVC configuration you would need 2 amplifiers, and I dont know of any 15kW car amplifiers.