Overkill for small room

One thing to think about is that smaller monitors with some subs may be more flexible in a smaller room. You can put the monitors where they image best and have the best overall tone. Put the subs where they interact best with the room. Since they’re two very different domains in terms of what’s happening in the room, there is some solid logic to breaking the speakers into more pieces rather than monolithic full frequency towers.

As long as you can EQ levels somehow, there’s no problem with adding speakers with too much bass capacity. At worst it’ll be wasted capacity. I’d be inclined to try to play that room sideways, assuming it’s ergonomically practical, which means some kind of treatment for the rear wall which won’t be far behind your head. I’ve got a 12’ x 20’ room and it’s much better played sideways. I like a wide and open sound stage and it’s hard to get that with only 12 feet. 14 feet is certainly better than 11. Of course if you can you should try it both ways. I’ll confess the bass was better when I played the setup on the 12’ wall. I was getting solid response down to 20 Hz. Now it falls off rapidly at 35 Hz before rising again for a while below 20 Hz. There’s real 5 Hz response, but what good is that with a hole between 20 and 35? It’s not too important to me, not as important as what’s happening up higher.

@asctim - interesting advice, as I assumed I'd set up the speakers on the narrow end, but I'll play with both and see what I like better.

Regarding subs, I agree. I've had huge speakers in the past (Acoustic Research TSW 810s I think) that did not need subwoofers! - we used to call them coffins. Anyway, those were tough to move from both a weight perspective and a room mode perspective (had large rear-firing woofers). 

I've since moved to smaller speakers (bookshelf) with a B&W ASW610 sub and I like the flexibility of being able to move things around more easily. As I prepare for my next significant upgrade, Ive been moving things around quite a bit to hear how the speakers and the room sound. When my new, smaller room is ready I can begin experimentation in there. Really excited. Sub is at least 20 years old and well used, so I'll consider replacing/upgrading (maybe 2) into the new space. 

I assumed I'd set up the speakers on the narrow end

I think that with your size room it would be better to place your speakers along the 11' wall. This will allow you to place both your speakers and your listening chair closer to the center of the room and away from the walls. You should try and keep a few feet if possible between your chair and the wall behind it.

The room will always be your biggest obstacle in achieving great sound. I would put most of my energy into learning how to either tune your room to your system (room treatments) or tune your system to your room (equalization) or a combination of both.

My room is 14' 4" x 10' 6" x 9'. I'm pairing small bookshelf speakers with 4) 12" subs. I play very loud aggressive music and I feel the highs are very clear and distinct, the mids are warm and natural and the lows thump but are not boomy.

continued excellent advice. I've got a lot to think about prior to the amp purchase, but the research and learning is a big part of the fun for me.  Thanks to all who have contributed helpful advice.

@audiorusty - I'm curious to know what you consider "very loud aggressive music." Do tell. And 4X 12" subs? What is your crossover? Are you feeding them with sub-outs or speaker-level? It must thump, indeed.

I’ve owned the special 40’s. They work quite well with Jazz, classical, and most vocal instrumentation. 
 

Electronic, rock, hip hop. Yes. They will play. Though they do not accelerate well with that style of music. At least that was my experience. Pass labs xa25, Herron vtsp line stage. I have zero treatment in my room, with the exception of wall to wall office carpet for my entire apartment. Maybe it helps. Maybe it hinders. Went back to my old speakers.  My little part of the world is good now.