Reply to KP3+Kontrol S2 or Kontrol S4

Hey guys, let me just say these community s have been very helpful as I've been a lurker for a while. Anyways. I have around $400 dollars right now and a KP3, so would you guys suggest getting a Kontrol S2 and use it with the KP3 or trading the KP3 plus money for a Kontrol S4? I'm really torn and I want to know if there is any real benefit of having the KP3 since the Kontrol series can do effects aswell. Thanks!