I consider myself an old hand at this. Great rooms like that are just not suitable for multi channel HT. Do not even try. In fact most domestic spaces are not suitable for surround HT, and would be better off 2.1 or 3.1. With that space you will get much better results with 2.1 or 3.1.
Great rooms are gathering spaces. Multi channel HT needs a dedicated space. Does that home have a basement?
Do not put a TV over or near a fireplace, unless you have in your budget frequent TV replacement. Heat is an electronics killer. The mount will solve the viewing angle, but not the heat, unless your fireplace is to be only for decoration and you will never use it. For new construction all fireplaces need to be condensing type and high efficiency, and will produce a lot of heat. They also produce condensate now and have to be connected to the plumbing, just like a furnace. Traditionally insert fireplaces have sent more heat up the chimney than into the room, but no more, the EPA have seen to that.
Your TV needs to be a along way away from any new type fireplace.
In a living/dining/kitchen type situation I would never put in HT and probably not even a TV.
This is what great room spaces are for.
Full blown HT takes a dedicated space.
We do have a 2.1 system in our downstairs great room.
But it is a long way from the fireplace.
In our little town home we have a living room that opens up to everywhere. The AV 3.1 is opposite to the fireplace.
So in a nutshell. if you want AV in that room build a nice 2.1 or 3.1 system away from the fireplace. Trying to put in a surround system will be a waste of time effort and money.
In any event you could make a 2.1 or 3.1 system with better speakers sound an lot better than the system you have now and a lot neater.
Since this is new construction you can neatly build everything in. New construction provides you with pretty much unlimited possibilities for neat integrated design. So use your imagination.
The 2.0 system in our previous home, which was new construction.
Lastly good sound is not determined by the number channels beyond 2, but by the quality of the speakers, electronics and implementation. These solutions allow for the use of much larger and capable speakers, and still have good cosmetic design and WAF. Now construction should allow for innovation to achieve optimal acoustic and architectural results.
It is your home change the floor plan anyway you want. It is not the builders home. In any event they seldom are masters of superb design, and are usually severely lacking in architectural skills. Control and lead them with a very firm hand.
