Dwhitt, Consider that your post gave unasked for advise that had nothing to do with the question, denegraded the posters equipment, AND was not responsive in any manner. Try to be helpful next time out, not just an audio oracle.
You could have said "Yes, you could probably connect two sub systems by simply splitting the signal from its source between the two sub systems (the reciever?) using a pair of 'Y' IC's. If your signal is coming from the speakers though, I'm not so sure and you might like to ask the manufacturer."
At least that is what I would have done. Oh, I guess I did, didn't I. :-)
And I would add, that the obtaining a second sub might help smooth out the bass because you would have a lot more flexibility of placement of the subs to compensate for room problems than just having one to achieve that. You could flatten out nodes, fill in nulls, have better sounding bass, but would not really get bigger bass SPL's other than the doubling of SPL's (i.e. 3db) by adding a seperate identical sub.
But I'm Newbee, what the hell do I know. Get a loan and buy a lot of new expensive equipment so you can learn to deal with more expensive problems! :-)