Alright, so this will be try number 2 to post this.
I just took delivery recently of an SVS PB13Ultra. It's a beast. A gorilla in piano black. I installed it and didn't tweak the settings initially and got several texts from my wife upstairs on the other side of the house that our chimney was rattling and to knock it off.
I use my theatre mostly for movies. I had a few guys over the other night who got me setup so I could do 2 channel if I wanted... I don't think it's for me. I've watched a few movies on it and I have been thoroughly impressed with the stately authority that is projected from this beast. I have it paired with a small Linn sub. While the Linn has a very large range, it doesn't have the lungs to compete with the SVS. But then, comparing the amplifiers, it's really got a fart's chance in a hurricane to keep up.
So movies...
Avengers - my setup really picked out the mixing problems. The SVS loved all the explosions. The music was very low in the mix. The voices were pretty intelligible.
Pacific Rim - mixed beautifully and who doesn't love giant monsters fighting giant robots? The SVS mowed through everything Mr. Del Toro was able to dish up.
The Last Stand - Honestly this had the greatest sounding shotgun blasts of any movie I've seen recently, even in theatre. Really enjoyed it.
GI Joe: Retalliation - Terrible movie, very well mixed sound. The SVS didn't care. It may as well have been playing the Smurfs. At this point, I really had the SVS dialled in and it was less a gorilla and more proud, and dependable workhorse, blending into the background when necessary and rising to the forefront when called. It's really an amazing sub.
I highly recommend it. Yes, I would like another SVS sub. Will I get one? I don't know. There are a lot of other purchases that I would like to get first before that and they're all really expensive.