I have one Ultra-X12 that I really like, but I feel like I want more "oomph." I see people saying that two X12's is a nice upgrade over just one. But what if I got an X13 as my second sub? Clearly, it would be more power to have one X13 and one X12, rather than two X12's. But would it be terribly noticeable?

Then again, one review talks about how impressively tight the bass is on the X13. What if I did most of my music listening with just an X13 (where I most value clarity), but powered up the X12 to work along with it during movies?

When I use REW in my room without a sub, I'm able to control bass ringing pretty well, especially since I picked up some acoustic treatments. But as soon as I turn on my X12, I get significant ringing at 20 Hz. Now I'm wondering if that ringing is necessarily the room, or if it could also be due to the sub?

The price on the X13 right now is quite tempting, so I'm trying to figure this out in the next few days, if possible.

Thanks!