I Just got from Guitar Center a Focusrite 2i2 and 2i4 which one do i need to dj from a laptop. Guys at store say to use 2i2 but the back of the box for the 2i4 shows a Laptop dj set up. I want to go from the computer to the focusrite then from the focusrite to the DJ Mixer then from mixer to Amp. I want to be able to cue up and listen to a song in my headset while I am playing a song over speakers. What Focusrite do I Keep?