I've got a thread in the DIY construction forum on 11.1, you might want to check that out, link here and in my signaturehttp://www.avsforum.com/t/1435778/moving-past-7-1-5-1-into-9-1-11-2-upgrading-your-ht-room-via-audyssey-dsx-or-dolby-pl-iiz
This visual from there may help you in planning:
Originally Posted by mtbdudex
I'm sure many here have built their Dedicated Home Theater to 7.1 (or 5.1) surround sound, did nice job pre-routing the speaker wire's in wall for integrated look, and lived with it for a few years.
This visual from my Denon 4520CI manual, makes it easier to grasp all the 7.1/9.1/11.1 speaker layout.
Here is the DTS Neo:X™ visual:
My room is similar to yours, but wider, 18.5 ft long x 14.5 ft wide x 8.75 ft high.
I also "echo" (pun intended) these thoughts, before going past 7.x, make sure you've done your acoustic treatment planning and installation to judge "are you missing something"?
As been stated here, for HT set-up this is the items you consider in order, so many people skip item 3, I don't know why.
1. Speaker location, 2. Listener position, 3. Acoustic treatments, 4. Electronic correction.
For me and my 7.1 to 11.1 reason, with my acoustic treatments honestly I have a great sound stage, no holes, and the sound does have 3D sense to it.
But, well it's a hobby thing also for me, and I have just enough width for wides, even then I'm going to better integrate them into my side wall.
Honestly your room will be the challenge for wides, unless you integrate them into the wall so they don't intrude into walk space.
Here is my install progress about 2 weeks ago.
I've got the heights mounted, the wides wires routed and they are sitting on the bar stools still as temp solution, not sure on final method for them.
I'm sidetracked just now with my multiple subwoofer upgrade
Once that is underway them I'll integrate these bookshelf speakers into the side walls, and re-do my side wall acoustic treatments at same times; everything is a system, you need to consider that viewpoint - acoustic measurements are a must to guide you.