Trouble getting both speaker and headphone audio w/ traktor pro 2 and rmx

I'm using a macbook, rmx + headphones, traktor pro 2, and two alesis m1 active usb speakers....and I can't get my setup configured so I can hear the song (one deck) playing on the speakers, and the other song (second deck) cued up on my head phones. Depending on how I tinker with the audio setup and output routing, I only get one or the other (both songs playing on the speakers when the audio device selected is usb output, and headphones only when the audo device selected is hercules rmx.) Ive been playing around with the audio routing (output monitor and master/internal and external etc.), but no luck. I NEVER had this issue with VDJ. It was simple to set up. Do I need a seperate sound card? Thanks for any help.