XXX on 400 watts sealed box on music 3" P-P excursion
Think what you want about your driver.. If you really want some honesty about it from an outside source check the data-bass reviews. This guy basically buys and has people send him super expensive drivers so that he can test them properly and see how they do.. Very measurement oriented, he has a great setup and he's no bias. As you can see, while the driver is good, everything I said about it is true. That video you linked didn't look like music either, looked alot like a test tone dropping in frequency, that's not music.
Anyway here is the review of the sub in a 4.5 cube box. Remember in a car you'll get cabin gain that will alter this response, but this is the basic starting response in an open field. "Using the XXX 18 driver in the 4.5 cube sealed test enclosure handicaps it substantially and results in a humped response shape with a significant roll off towards the top end. Sensitivity is very low due to the high moving mass and low BL^2/RE of the motor. This driver wants an enclosure many times this size for a maximally flat alignment. Additionally the huge excursion levels supported require tremendous amounts of amplifier power to make use of them. Power levels that are likely not realistic to use. Distortion performance below 50Hz is pretty good considering the output levels reached but would probably improve substantially in a larger airspace. On the positive side the chance of running out of excursion with this driver in a cabinet this small is next to nothing using any sort of typical amplification scheme. This driver is much better suited to larger sealed enclosures, giant vented alignments and probably most of all IB. "
anyway
http://www.data-bass.com
Again, not a terrible driver but the car brings out this drivers weakpoints even more. The peak near 30-40hz that this driver naturally had due to the heavy coil and high inductance is right where alot of cars have alot of gain. Most cars have nulls between 60 and 80hz where this driver won't play. Your going to have probably a 20-30db difference between 80 and 40hz hz in a car. It's an expensive speaker and it can be a good one, but really this thing is built for a HT system. If your goal is 10hz at 120db's this thing can deliver, if you have the room. Check out the measurements of the ported setup they tried 30+ cubes at 12hz tuning, that's where this thing shines, stupid big boxes tuned very low. Even in a box that big, plenty of woofers can provide more output ABOVE 30hz in a box iiterally 1/6th the size, which is where most music plays. This may not be a problem for you, assuming you planned on crossing your driver over at 40-50hz. Really it depends what you wanted out of the speaker in the first place. I just know alot of people are very disappointed with these things when they get them into the car. Not because it's a bad speaker, but it's not really designed for musical playback, let alone in a vehicle, despite how RE markets them.
Between the new and old XXX the power handling is difference isn't super significant. The XXX used a fairly beefy 3inch coil, most users put 2-2.5k on it without issues. XBL^2 also makes the driver very effecient, as it doesn't lose motor force as the coil leaves the gap. That kind of effeciency you wont' see on a standard t/s sheet, it takes real world testing and measurment to see that.
Anyway back to your setup, what other speakers are going into the car, what kind of car?
