Well, the upgrade to the X-LS was fairly large-scale. It uses a new tweeter that will eventually be in production but that I don't think is shipping yet (which by itself adds almost $100 to the price of an original X-LS), it includes a different crossover design in addition to using significantly more expensive components in the crossover network, and it includes adding dampening material to the inside of the enclosure. That's why the price for an already-modified "Ninja X-LS" is $1000 rather than the $300 that a stock X-LS will cost when the new tweeter arrives.