Setting up an external sound card for recording

Hi guys!

I've posted here once before when I needed help linking my Macbook Pro (w/ Traktor Scratch pro 2) with 2 CDJ 400's / DJM 400, which is working awesomely now and love it.

But I'm wanting to record my mixes, I've already attempted to try hack around with garageband and audacity to try record via desktop computer and the Mac but have been unsuccessful. ( Was picking up noise from the room not through the outputs of the mixer )

I have a Numark DJ IO which i've tried to use as the sound card for Traktor (I believe it only works for Virtual DJ can anyone confirm ?) , but haven't been able to get it working.

I'm believeing of purchasing a Audio 6 soundcard by NI but my biggest fear is that there isn't any 'Recording/booth etc ' ports of the back of DJM 400. and all the videos/tutorials I've seen mention them.

So where I am getting is, I need a way that I can record my mixes, I can record internally through traktor, but it plays the song being cue'd at the same time so thats no good.

I'm losing hair over this, please help. lol

Thanks, Rex.