I have a y-cable right now that goes to my pb12/2 ultra and the other end goes to my buttkicker. I am considering a second ultra, but how would I hook this up? Would I simply get another y-cable to attach to one end of the existing y-cable that is in the sub out making 3 lfe out's? Is this the best way to do this, or is there a better way? Any downsides to dual y-cables?