Unfortunately you are new to this and don't realize what a monumental challenge this represents. Your room dimension are not a domestic space.
Now speakers can do well in small spaces, but they do poorly in large ones unless you poor lots of resources at the problem.
You stated you want high quality room filling sound. The only way you can do that is with a very high quality and powerful stereo pair that can generate high sound pressure levels.
Now there are probably no more than three members here, if that who have experience in this type of challenge. I have had some experience and have designed and built high definition systems for large spaces.
Now lets get your multiple speaker idea out of the way first. This will not give you high quality room filling sound. The reason is that sound travels pretty slowly. Distributed systems can work well for speech and background music. However the volume of each speaker has to be low, so that everyone only gets almost all the sound from one speaker. If they hear all of them then the time delays makes everything garbled and very low quality. You can NOT fulfill your aim with this approach. In addition the sound must be mono and not stereo.
The next approach is the central cluster. This can work well and give good clarity but again the sound is mono.
The only way to get what your aim states is with a pair of expensive powerful pro speakers, that have an exemplary dispersion pattern, a very smooth frequency response, and very low Q bass tuning. If the bass is at all resonant you are dead for quality. The usual method is to use a large bass driver, and a good sectoral horn actively biamped. There is no place for passive crossovers to fulfill your stated criteria.
My approach, and this means a custom design and build, is to use a low Qts 15" drivers in enormous back loaded horns with 3' horns mouths and use a line source with at least 8 drivers in vertical line above and biamp it with electronic crossover between 400 and 500 Hz. The reason being that until recently the top end horns have been highly problematic. The speakers I specked for you have a specification that would I think obviate the need for a custom line array.
In Engalnd close friends of my wife's sister live in a very old medieval church deep in the Malvern Hills. He is heir to the Bulmer Cider fortune. This guy sold out the company for a fortune. He has degrees in physics. He is highly intelligent but very eccentric in a unique English kind of way. I just love this man's company. He has converted the old bell tower into an astronomical observatory. He makes in own telescopes, including grinding and polishing his own lenses.
Anyhow the kitchen is where the alter was, and the bedrooms in the choir balcony. It is relatively small for a church. However attempts to get good sound in the living area have alluded him and he has now abandoned it. He is a very wealthy man but unwilling to commit the resources required to solve the challenge. He has put a decent system in what I think was a small side chapel at ease.
So I think you have to rethink your goals and see if you can get what you want within a budget you can afford.
I strongly recommend you seriously consider Mr Boat's suggestion. The other alternative is to construct a low volume background music system.
Lastly if you do want to go for a high quality system you will need to budget for acoustic treatment, or you will waste your money. From the description of the ceiling hanging sound absorbers will likely be required, like the BBC used in the RAH.
Those you might not like the look of in your home.
