JL Audio

Music get one 112
Movies do the 113
Depends what you listen to.

The 110 doesn't have enough punch.
That is just my 2c ymmv.

I use two F113's. The point is not to shake the walls but to even out the frequency response in the room (always easier with two subs). I would buy one F113 now and when funds become available buy the second one later. You can run them in stereo (master/master) or as master/slave (which I do).

By the way, if the walls are shaking and you are not watching the pod scene in War of the Worlds you are running them way too hot and/or you have room mode issues to fix.

One F113 will be better for HT than dual F110. The one
F113 will go lower with more clean output!

I have 2 x f113 in an identically sized room. Walls are not shacking at all. Just clean tight bass. Get one f113 first, and when funds permit get a second and run as discrete stereo pair. Always nice to know there is an upgrade path down the road. Getting 2 x f110, be done with it and always wonder what 2 x f113 would have been like is plain audiophile torture IMO.

I agree with pgeek.