Reply to question regarding mac pro retina not having am audio in port

Hello

I am a newbie trying to transition my Djing from a hobby to the next level.

currently, I have an ASUS, Traktor pro2, Traktor s4, and a MF spectra.

I'm looking into buying a new laptop (mac pro retina is in my mind) since my laptop can't handle all the things I want to do.

With asus I would connect from s4 master out into my laptop's audio in jack, use laptop as a amplifier, and connect my speakers into laptop's headphone jack.

I read that the new mac pro retina 15" does NOT have a audio in jack just the headphone jack.

How would I connect my set up into the new mac pro retina?

Thank you.