Hi everyone I have an home theatre (here in Québec city Canada) of 23 feet long by 11feet large,I have Outlaw 7900 with Integra 9.8.My speakers are: front Paradigm studio 100,center Paradigm cc-690,suround Paradigm studio 60,suround back Paradigm studio 20 and finaly 1 Paradigm servo 15 v2 for the subwoofer....I have also 2 buttkicker LFE with the Buttkicker amplifier so...I read a lot on this forum and everywhere on the net but I need to have clear answers...
I would like to change my subwoofer and I hesitate with few options and models:
1-buy another Paradigm servo 15 v2 (2000$ canadian)
2-buy 2 new Paradigm subb 15 with perfect kit (5000$ canadian)
3-2 SVS PB13-Ultra (4500$ canadian)
4-1 Elemental A7 - 900 Subwoofer (it is very very big maybe too more,but if is the best for my buck...why not.I ll wait for the shipping cost)
5-2 Seaton submersive (again I ll wait for the shipping cost)
6-2 Jl audio PHATOM f113
It is probably the last subwoofer I am gonna buy so I wont the best for my buck......I REALY LOVE to feel the bass,I think it is the number 1 priority in a Home theatre....I use it movie and videos game 75% and music 25%..
I need your comments on this...before I take a decision to made the best choice ,cause I cant listen none of all those subwoofers and it s a lot of money....Thank you everyone....

They all look good, but while I would love to have the sound of the A7-900, I would hate to have to move that around. At 400 lbs, I don't even know how you would be able to move that around. Since money doesn't seem to be too tight for you, you should consider the Seaton terraforms also. Maybe a HSU ULS quad drive. Of all the choices you listed, I would go with either the Submersives, or the Phantoms. The Phantoms would have less output, but they are so damn pretty.

If you can afford it, 2 separate subwoofers are usually better than one. You can place them in different locations in your room which will help get every seat in your theatre similar levels of bass. I have a single ultra which is awesome, but due to my room some seat locations get much more bass then others.

I've never heard the submersive, but based on it's reputation I'm thinking two of them spread out in your room will give you the most balanced/gratifying bass out of the options you have listed above.