Reply to audio 6 or audio 10?

I'm a bit stuck here looked everywhere for a clear answer, but don't find it.

Want to go back to two deck setup with traktor scratchpro 2 and sample decks.

so my db4 is coming in and still not certified, what would be my best option to mimic a bit of my s4 style.

Set up: db4 mixer, two denon 3700's for decks and a kontrol X1 for sample decks, to get use of spinning platters i'll need an audio interface.

I would say, audio 6 would be ok, but if i look at the audio 6 it has 3 stereo outputs so 2 for the decks, that would leave me one for sample decks on my mixer. So one mixer channel would be unused, is it possible to get sample decks work like over two channels like the s4 with audio 6? (make any sense?)

I will buy upgrade traktor scratch pro package for the s4, cheapest option and separate audio interface (bonus extra traktor pro 2 copy i could sell).