Hi Nick,
It's "generally" not a good idea to mix subs of different models. Differences in the phase response and frequency response inherent to the two subwoofer designs will likely cause more issues than benefits unless you have a lot of time/tools to measure and align them (over my head for sure, but others on here could explain if you had a good measurement rig and the space to do the measurements, which it doesn't sound like you do).
If you're wanting to use your TX2181 subs in a cardioid configuration, all you need is at least two channels of amplifier, some digital delay for one of them, and a polarity reversal (special cable at it's crudest, off the board or amp would be better for experimentation). I don't have an M32 but i suspect it would have delay on it's aux outputs, so you could run your subs on a pair of aux sends (one with the appropriate processing applied). EV has a good guide for determining just what that processing needs to be online here:
www.electrovoice.com/downloadfile.php?id=8913There is no way to utilize the processing inside your powered EV cabs to make your other cabs act the same way that I'm aware of, if that's what you were asking. Hope that helps!