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
I would absolutely not attempt speaker changes for this. Those are fabulous speakers, but maybe a second sub.

The very first place to start is room acoustics:

ATS Acoustics
GIK Acoustics

Wall panels will reduce mid/treble hash and output, and improve clarity.  Bass traps will make room correction work better.

Regardless, seal the main ports and re-run the room calibration. You are allowed to raise the bass level by the way, if you don't like the end result.  This will reduce amplifier strain, Doppler distortion and driver excursion.

After you have done the room calibration, a second sub could be really good if you have flexibility in placement.  If you want to simulate this, try Room EQ Wizard's room simulator. 
PS _ You can also use REW to help you place your single sub more ideally. That is also a good thing to do before buying anything.
Won't need to spend anywhere near $15k but go for it if you must. Won't need to though because when it comes to bass more is better than better. In other words don't buy one or two subs with your $15k, buy three or four. 

Hard to believe I know but Duke had a customer with a $30k sub budget who compared and went with four of his Swarm for $3k because it was better than any one or even two subs he could buy for $30k. So if you must spend the money then get four. 

I'm saying this fifteen different ways because its so darn hard to get people to understand. Once they do, every single one who does it is blown away. Basically, there is no amount of money you can throw at this problem that will solve it as good with one as you can easily do with four, and for much less. Do a search. You will see.
I think the first two responses you received are very well-informed and that's great to see/read. Although Monitor Audio is not for me they make great speakers and you own some. I'm surprised they are not dynamic enough, but subs will help. (Possibly high pass to the Gold 300s very low 50-60, to relieve 40 and below, and to play louder at higher Hz? I never had success but who knows; they say it can work.)

Room treatment is a good recommendation (I still need it myself!) with which I fully concur. Well done treatment works wonders. Good luck.

Get the subs for that rock-solid foundation to your music and movies. I need to read more about 3-4 subs versus one big one, or two. That Audio Kinesis Swarm set of four is supposed to be quite effective at 25oo or so. Along the same line, 3 or 4 well-placed SVS SB-2000s barely discontinued, each with it's own amp and room location. And there are plenty of deadly single subs out there.
@musicaddict - I've never heard a system, crossed at 40 Hz which didn't sound better crossed at 80 Hz when properly done.
Appreciate the responses. I have tried different crossover settings for Monitor Audio Gold 300s and find 60hz to be best with my current Paradigm Sub 12. 80hz may work better though with 2 or more subs.

I could get 2 additional subs and put the Paradigm at the rear of the room. I'll check out the subs you mentioned and see about 4. I've been told and have read, more is better. My concern is to get a good balance with speed and accuracy for music and decent rumble for movies. 4 smaller subs may work better .

Thanks for the input.
Nice speakers, however, I am not a fan of ports. If any, front facing for direct radiation of bass fundamentals and their overtones supporting definition/imaging. Not indirect diffuse multi-reflected sound waves as you have now.

You want to test/listen in 2 channel mode, not surround sound, no center, no sub, no surrounds, do that last.

As Eric suggested, I would start by temporarily closing the rear ports. It will not effect the mid and tweeter. It will effect the two 8" drivers.

Play something with distinct moments of highs, mids, and bass first, then temporarily cover the ports, what differences?

Now, are you wanting extended directional bass, or simply extended bass?

My home theater, I use 1 self powered sub, in a non-directional way, to simply add the dinosaur stomp in Jurassic Park, that kind of thing.

For music, bass is/can be stereo/directional, that requires a pair of front firing subs located adjacent to the mains. Self powered. Now you will know where the bass player is standing.

Balance the subs with the mains only, i.e. 2 channel with bass extension. Then, add the center and surrounds. Avoid too much surround volume. Generally (i.e. not specific helicopters from the rear left) you should not be aware of them until you turn them off and the sound collapses to the front. Many people have them too loud.

Keep in mind, much content has been altered along the way, If something is not sounding great, I switch to 2 channel mode, often find it better.

Those are nice comments about dialing in the speakers, Elliott... I really like the idea of blending the sub properly with the larger mains first, then adding the other three, etc. Even better if the system does double duty for two channel music.

I would not be surprised if you are correct about the 80Hz crossover, Erik. It seems everything I run for mains is relatively full-range and my sub is probably too muddy so I shelf it down low. I should try fiddling a bit in the home theater with sub & main crossover points, and shop new sub(s).

I am going to start actively reading about setting up several smaller subs in our theater, small at 12 x 22.5 x 8. I can 'hear' two or three 12" powered subs making that room come alive.

In the music room the D2s drop into high 30s; I run them full-range, not yet finding a good way to blend a high pass to them. Best with an REL B1 is 23Hz and 9/40 on volume. Smooth down to almost 25Hz, no concert volumes though, thank you.

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.
Sorry to ask this question, but what is REW, where would I find the tool to use it?

Okay got it 
Room Equalization Wizard.
REW. Now where to get it and I'll do some homework.

Thanks for the quick reply. I'll look at some room correction options this weekend.