One thing is...the youtube video has the older version speakers. Mine is the newer 08 version.
And there is likely the entire reason for the difference. Different driver designs, materials, etc... will have very different excursion levels. If I had to guess at the reason you don't see as much movement (provided again that you are setting yours up exactly as the ones in the video) is they may have moved to a stiffer and more durable driver due to returns/replacements of the previous models. Like almost everything in speaker design - it's a set of compromises.
What you should be more concerned with is how they sound to you. If you think they sound great, but are disappointed that you can't make your own video of flagellating woofer cones... then just go buy a cheap pair of cerwin vegas and power them with a budget car amp and shoot your video. Then go back and enjoy the music coming from the monitors in private.
On the other hand, if you have a significant problem with the sound coming from the monitors... then you should try addressing that with the manufacturer or dealer immediately. Cone excursion is not the signature of accurate bass (or even necessarily deep bass, just LOUD bass) - sure it's fun to watch, but some of the best speakers I've heard had drivers that were barely moving visibly. Of course, much of that has to do with what music I listen to and perhaps if they'd been fed some techno with overmixed synth-bass they might have been bouncing all over the place.
Not to mention I value my hearing so I have never taken any nearfield monitors and turned their volume pot all the way to maximum... I find it difficult to believe the sound coming from them was superior in any way (despite the fun woofer-dancing).
