Reply to S4 and Xone K2 for ableton/traktor setup

I have tried countless times to configure a stable ableton and traktor combo using my s4 and its built-in soundcard but have always run into problems, either with unwanted feedback or the channel faders failing to control the output of each deck. I presume this is something to do with the soundcard of the s4 as I know it is possible using something like the audio 10 interface.

I was considering buying an Allen and Heath K2 as an extra effects controller and wondered whether its in-built soundcard would help my situation in any way?