funky

I currently have installed in my 2006 QX56 an saz-1200d and a sa-15 d2 in a ported enclosure 3.45 ft cubed tuned to 35 hz. I have 0 gauge running to the back the big 3 all in 0 gauge. I have an xspower d5100r up front and a d680 on the way for the back, gets here today. My stock bose actually over plays my current set up so probably going to leave it like it is until I have to upgrade as everything ties into the stereo. I found a deal I could not pass up on a saz-1500d v2 and now have to attempt figuring out how to make the right upgrade to make my SUV pound. What would be a way of setting up a system with these 2 amps? I was thinking of several ways, but would like to hear what would give me the most with what I have. A couple of my main thoughts are what impedence subs? How many? Should I use both 15's and 12's in seperate enclosures? Basically I need help figuring this out.