Building a house

Like me you are really fortunate to be able to start from zero with your listening room.  I had been doing hi-fi for 50 years before my chance came.
There are already some great suggestions above, so I won't repeat any of those..

My room is in the basement.  As I've said in other posts this gives real advantage by enabling all equipment to be in hard contact with the floor/ground so it cannot move or vibrate, causing distortion of the signal and corruption of the soundstage.  Ensure the mass loading is maximised by using heavy support materials.

A basement siting also removes the temptation to include windows.  Glass is about the hardest most reflective substance there is and can reflect sound waves behind curtains and blinds.  Concert halls and recording studios don't have windows.

With an empty page, acoustic design starts from scratch.  So there is every chance to get it exactly right.  There is a temptation to over-damp with thick layers of padding on the walls and thick rugs. Even ceiling treatment.  This is not the best way to go, some sound reflection is required, to create a realistic soundstage and room boundaries.  So I very strongly recommend paying for an acoustician with relevant expertise and experience to advise; the price will be very small relative to the overall construction cost.

Prepare for a shock.  You will have a bigger sound quality upgrade than an order of magnitude more expenditure on equipment, wires, tweaks, the lot.

AVOID a windowless basement!

I really appreciate all of the great advice and thoughts. The house will be 1 floor and no basement. Fortunately my wife has a hands off approach to this project (she gets to do the rest of the house). The room will be rectangular with 12 foot ceiling. Several of you mention the "right proportions" - opinions on what these proportions are? Thanks again!

Do you have a turntable that you will be using for more than 50% of your listening? If yes look at isolating the turntable. You will loose the option to move it but I had a cement pad installed into the floor that is suspended or supported by the foundation walls not the floor joists. I have no vibrations or issues when someone walks in the room. The other method I have heard of is creating a support stricture in the wall studs tied into the foundation for a wall mount turntable bracket.
also don’t forget to run quality Ethernet wire for internet connection. Wireless is only a tool of convince always hard wire your streaming source.
Lighting I mounted crown 6 inched down from the wall ceiling intersection and dropped color changing, dimming  led strips. This allows you to create any mood setting you like.

- The planning phase is where you determine that ultimate potential that your room will have. Your system will never be any better than the room will allow it to be.
- I've been designing, calibrating and treating systems and rooms for the past 14 years, and it's much easier to work it out on paper/computer than to "fix" it later.
- Proportions are absolutely critical, so figure out the max footprint you have to work with and then work through the various tables that give you best-case scenarios for minimizing standing waves for a room that will fit that footprint. All else being equal, a bigger room is better to a point, as the severity of modal problems tend to be less in a bigger room.
- Ideally, try to acoustically separate the room from the rest of the house if you have anyone to answer to for excessive SPL's - money well-spent on the room versus spending it on a lawyer later. This includes structural isolation and acoustic treatments. If you're doing a slab floor there are ways to isolate and properly treat that. If you'll have a wood-framed floor under the room, be extra careful in the design phase, as a wood floor system becomes a type of passive radiator with a very substantial resonant frequency that can ruin an otherwise great room.
- Pay attention to what the eventual decay time (RT-60) will be in the room - this can be approximated by computer model, and there are guidelines for what's appropriate depending on whether or not you'll be listening to 2-channel music or surround sound A/V.
- Be sure to make the back of the room slightly more acoustically "alive" than the front.
- Expect to balance diffusion/absorption/reflection with room treatments in the final phase - all the computer simulations in the world won't be any replacement for in-room measurements and calibration once the system and furniture are actually in that room.
- Home-run 10ga. feeds to the head-end outlets, ideally from an isolated sub-panel.
- Glass isn't nearly as bad acoustically as one might think, but it does tend to let in a lot of outside noise, so I'd try to minimize the glass and keep it away from the front of the room or the first reflection points.
- And finally, if you can design the room to include infinite baffle subs...do it! I built my home back in PA 24 years ago, and was able to integrate infinite baffle subs into my listening room, and have used them in a world-class ground-up listening room build, and there is nothing like them. Effortless bass down to 10Hz, magnificent harmonic richness that carries up into the midrange, unmatched punch and dynamics. I moved to NM 4 years ago into a house with no IB option, and not a day goes by that I don't miss them. You have to design the room around them, but if you can pull it off, you will be rewarded. Be sure to computer model the room and place them properly in the design phase, as they become part of the structure of the room and can't be moved in the future; putting them in an acoustic null or peak will be a problem that only EQ can minimize, and that will neuter the bass.
- Take your time and get it right now, and you'll enjoy that system forever.
Hope that helps!