Ok so I wouldn't say I'm new to DJing but I need some advice on what audio card to get because I'm most definitely not a pro or a guru.

Currently my set-up is Traktor Pro with a Hercules RMX controller and the Behringer DDM4000 Mixer (ya I know not as cool as I would love it to be). I'm using the RMX as my midi controller and as my external sound card and the decks are then routed to 2 separate channels on my mixer.

Well you see here I really want to get into 4 deck mixing and I know I can use the DDM4000 and the RMX as separate midi controllers to control the 4 decks and w/e else I want. What I really want to do is use the RMX to control the 4 decks via my own .tsi that I wrote and then route the four different channels into the mixer (I like mixing externally for some reason). So I would thus need an external audio card to do that. The problem is I have no clue what to get.

Another solution to the problem is to mix internally with Traktor using the DDM4000 as my midi controller for the separate decks then have my master routed through the audio card. Then the RMX can be used as a controller for looping, effects, ... etc.

Personally i feel that I have absolutely not a clue about what I'm talking about so if anyone could help me find a viable set-up for what I want, it would be much appreciated!