Reply to External Mixers and Traktor (Xone 42) ?

How would it work with Traktor Pro 2, In how what are the advantages and disadvantages of buying an analogue mixer and only using with Traktor Pro 2. What do you find you get and what you do not get from it using it this way?

Had thoughts of using this mixer with an X1.

Does the USB port on it send Midi to the software to control from your mixer what happens on screen?

It needs external Sound card Im sure, but which one of the Native Instruments range would suit me? Ill just be playing from MP3s in Traktor not a CD or TT's.

See Ive been getting very confused on how External mixers work with Traktor