Reply to Really Stupid Question

I know this is a really stupid question, but I can't remember how this works. I'm buying an S2/S4 soon and I want to be able to run a midi fighter, and possibly a maschine, and 1 or 2 of NI's other controllers (F1,X1,Z1).

How many channels does the S2/S4 have? Would I have to run an external sound card to be able to have all of this?

Thanks! (sorry for the stupid question)