Reply to Studio Monitors + S4?

Alright so I just bought two KRK Rokit 5's. I was under the impression that with studio monitors I would need a soundcard/monitor management type hardware thing to be able to use them. Well I called up a few places (Guitar Center and Sweetwater) and they said that I can use my Traktor Kontrol S4 as my soundcard and route it directly though there.


Now, I can see how this could potentially work if I was using this for solely DJing, but I would like to listen to music through the monitors as well and it would be a serious pain to route the computer through the live input in the S4 as well just to be able to hear a song.

What can/should I do? I feel like this just causes confusion.