hey andy
i went from a timecode setup with 2 decks with a soundcard using various softwares to a 4 deck setup with the s4 and traktor pro2.
from my experience things become less reliable and dont work smoothly when you start adding bits of kit from different manufactures when using a laptop, the set up for it all becomes totally custom and you’ll spend hours trying to get it the best you can.
there are a lot of places that do 0% finance for dj kit if thats an option?