Reply to Mixtrack Pro Question

I just recently got into mobile DJ'ing for family gatherings and parties, my setup is currently a mixtrack pro outputting to a seismic audio LE-3000 powering two seismic audio SA-15's.

It's outputting good high's and mid's, but it's lacking the amount of bass I desire. I want to get one of SA's powered subs, but to my understanding, the 2nd set of outputs on the mixtrack pro is only for the cue channel. Is there a way to make the 2nd output on the mixtrack pro mirror that of the 1st? I don't want to find out after buying a sub that I can't use it with the mixtrack pro. And, if I can make the 2nd set of outputs on the mixtrack mirror the first, can I still use the headphone jack on the front of the controller as a cue channel? Thanks for reading!

Also, my SA-15's have daisy chain outputs, could I just plug a powered sub into one of them or would that be a no-no?