Reply to Numark Mixtrack external sound card?

Ok i just got the numark mixtrack, love it for the price... but... i bought a turtle beach amigo ii sound card well got it free, anyways when i wanna plug in the speakers i plug it into my macbook pro headphone jack, but i put my amigo ii to my usb plug in my headphones i can hear nothing.. even when i switch it makes me use one either speakers or headphones. Im trying to dj so when i hit cue for me to hear the other song it wont play through the headphones but u will hear it on the speakers which makese me look pretty dumb. I dunno if the zalman 5.1 external sound card would work. I have $20 to spend on a soundcard to work... any sugestions?