Reply to Can the S2 connect with a mixtrack pro with a soundcard?

I have a mixtrack pro with an internal soundcard and my buddy has a S2 and we've been believeing about djing together. Here was the idea: we would both have traktor running on our laptops and have our output in sync through midi. We would virtually be on a 4deck-type controller by controlling tracks A&B on one mix deck and A&B on the other which would serve as C&D I guess. We thought this would be cool because one person can be preparing cue points and samples or other prep stuff while the other person is mixing. I also wanted to have ableton open for samples/loops(also synced through midi) even though my buddy and I would have our own sample decks on top of it all. But we don't have a soundcard and I was wondering how exactly the wiring would be set up?
I was believeing from the controllers' outputs to the inputs on the sound card and then a rca connected from the output of the soundcard to the speaker receiver input.

Here's my concerns/questions before purchasing
-Ableton doesn't recognize my mixtrack pro's soundcard so I'm scared the sound card I buy won't either.
-Which laptop would the soundcard need to be plugged into? Would traktor still recognize the soundcard just by being connected through rca?
-Would it be possible to sync ableton with both the running traktors?