@Flavio > It's not the sound card you need to use Traktor effects, it's a controller to use with the Traktor effects. If you had an X1 you could control the Traktor effects with that. But personally, I wouldn't bother because you have superior Sound Color Effects and Beat Effects on the DJM-800 alone.
You don't need an Audio 6 unless you want to use Time Code with Traktor. You can alternately use the USB outputs on the CDJ-2000's and assign them to directly control the Traktor Decks and simply remove the Audio 6 and time code from your setup. Even if you really feel you need the X1, you still don't need the Audio 6.