I can tell you what has been recommended to me, but I can't comment yet on how it will sound, given that my new room is still under construction (see my build thread for details).
My room acoustics were designed by Keith Yates Design Group. In a clean-sheet design, I believe Keith would have probably specified Genelec speakers, but I had my Aerial Model 9s and my CC5 center which I chose after extensive listening tests, and I wanted to stay with them.
So, starting with the three Aerials up front, Keith specified three Seaton SubMersive HPs as the primary subs, combined with four Velodyne SC-IW in-wall subs to help even out bass response throughout the room. I believe he has used the Seatons on other jobs as well.
So, to me, that's a pretty good endorsement. In a few months, I'll be able to tell you how it all turns out.
Now, that being said, I have heard the SW12 in action and it was very impressive. In the demo room where I heard it (combined with 7Bs), we actually blew a light fixture out of the suspended ceiling during the War of the Worlds scene where the machine emerges. I think it's quite a good sub, but on this I went with KYDG's recommendation.
If you should decide you're interested in one or two Aerial subs, PM me. I have a pair of SW12s that I bought awhile ago, before I started to work with KYDG.