I am a little lost as to what you are trying to hook up to what and with what intended result.
You say you have an S4mk2 with an unreliable PC and you want to switch to Mac. Then suddenly you mention starting with an iPod5 because of trying Traktor DJ. Are you saying you want to stop using the S4? Do you want to use the iPod5 with Traktor DJ instead?
In the last case, you would need a DJ splitter cable to get sound to your speakers and your headphone.
You mention a provided cable. But what is it provided with, what is it supposed to connect from and to?
Let us know so we can better answer your questions.