Dual subs and or speaker uograde

I have Monitor Audio Gold 300s as my front mains. All Gold speakers 100s for surrounds, 300Gx center, Gold GX rear surrounds.
Paradigm Sub 12 Reference as my sub.

Room is 10'w at front, and 18' wide at rear. 7.5'H, 22' long and 13' from front wall I have my 3 theatre seats,

I feel I need a little more umph for watching concerts on DVD.

I have about 15k to spend.

I am considering dual Persona subs or dual B&W DB1D subs to augment bass.

Other option is Persona 3F with 1 Persona sub ( a little over my budget) or Persona 3F with 1 B&W DB1D sub (on budget) or Persona 3F and 2 SVS Ultra16 subs.

Another options is GoldenEar Triton Reference, but due to 10' front wall with 100' screen, I'd need to put speakers fairly close to front outside walls 10-12"

Appreciate your opinions.

My audio store sells all except GoldenEar. They have given me great service.

My amp and preamp are NAD M27 and M17. I'm happy with the quality of the sound of my Monitor Audio 300s. Great sound. Not enough umph.

Thanks Roger
there's a good thread from earlier this year,  where Duke talks about subs with tower speakers, sometime two subs sounding great,  and they don't need to be identical...
Looked up the Audio Kinesis Swarms. Sounds interesting. 

Room treatments would be good. I have an issue with the room, it's not square/rectangular.

The one long wall runs straight for 22' front wall with projector is 10'6" wide then the wall parallel to the long wall runs about 5' then I have a bannister with wooden spindles for the staircase going to the front entrance. Then besides the stairs it has an opening at bout 3'6" to access under the stairs then a door to the garage, then the wall does a 30 degree turn back into the room then runs a couple feed parallel to the long wall then widens 4' turns a 90 degree to two other doors to the back wall. The back wall parallel to the front wall is about 18' wide. 

The main issue for room treatment would be the front part of the parallel wall beside the stairs.

The right front main is just behind the bannister. There's no wall (just an open staircase with wooden spindles, so I don't know where I'd put any room treatment on that wall by the stairs. The long wall would be doable. Bass traps couldn't be too wide at the front wall because of the 100" screen. They'd have to be put in the corners with a round front side.

I am not too familiar with room treatment so I'll have to watch some videos on YouTube and do some reading. Hopefully it wouldn't kill too much volume as I like to watch music concert videos pretty loud.

Thanks for the info.
Just FYI:

There's no truth to the idea that smaller subs are faster.  They just won't exacerbate the lowest octave as much.

I strongly encourage you to play around with REW's room simulator. It will help you understand placement, and options without lifting and shifting.

All the talk about how fast some subs are is pure blather. I can outrun almost all of them.
I have 4 in my home theatre huge change from one ,I have two in my dedicated audio room but am remodeling a stand alone 16'x24' building on my property just for dedicated audio .I will run four there when complete. As Erik stated the single biggest upgrade I did within reason was treatment period.