I took a very quick look at the DJM 250 and didn't see anything about a built in sound card...If that's true then you must have an external sound card to hook up to between decks and Traktor (laptop).
If you are a Traktor user, I would look at a DJM that has a built in sound card and then compare the price to what it would cost you to go with a basic mixer and an external sound card like the NI Audio 6, 8, 10....
As for the X1, it is basically a controller to control Tracktor's decks and effects so once again, you need to figure out your mixer side.
Cheers