House buying and the aspiring audipihile

+1 on Master Bedrooms as listening rooms. I think they are the largest closed space typically available in a house.

Though my current listening setup might be duplicate for you due to the unusual shape of my master bedroom, I'm sharing this in case you come across something similar. Our house was built in 1998 and we've lived in the house for over 8 years. Our master bedroom is essentially in the shape of a hexagon with a bit of inset where our queen sized bed is located and an inset directly across from the bed. The length of the room is 18.5 feet. Each side of the hexagon is about 11-12 ft. The room has an 8 foot ceiling. My Monitor Audio Silver 300 speakers are 18 inches from the front wall.

Interestingly I've only figured this out in the past year as my wife used to have a TV in our bedroom, To improve her sleep, her doctor advised her to take the TV our of our bedroom. That opened up the wall opposite our bed for my audio system. I originally thought that the hexagonal shape would be difficult to use from an acoustic perspective. However, what I realized is that the hexagonal shape of the room naturally seem to absorb stray reverberation. There is only one 1st order reflection coming from the left speaker which I've been able to absorb with an acoustic panel. The result has been a room that sounds intimate, precise and pretty acoustically quiet..

I would encourage you to take a long look at basement spaces. Yes, in the South I think you would be looking for high ground or some pretty tall cable-lifts. Typical foundation walls are stiff enough to contain everything so you can “treat” the room with whatever materials and maybe break up some 90 degree angles. Good start on soundproofing and isolation. Usually handy to the mains breakers. 
Add: Dehumidifier

I'm happy with my Atlanta Metro home with finished basement (dry-walled, carpeted concrete floor, dropped ceiling with heavy-ish fibrous material squares) which has a decent sized room for dedicated audio (20.125' L x 12.67' W), EXCEPT for the ceiling height (7.1' H)! Would really like 9' or so instead. That is my room's limiting factor. It could prob use a little more width as well, but not as much a concern as ceiling height for me. But very happy with the sound from the room, though it is treated with GIK products.

@ejr1953   Congrats on the Asheville home!  That is on my short list for a perhaps final home destination.  I love it for all the reasons you cited.

I'm actually surprised how good some rooms can sound that aren't "supposed" to sound good.

I am outside of Austin. Arguably one the best town in the country for music. Big reason for which I made it our retirement home. And now with my new house of stereo it pretty much sealed the fact that we will end our days here.