Audio room floor question

You do not want to put any wood in contact with concrete. Plastic vapor barrier, filled with holes, will not prevent the wood from quickly rotting. Sleepers over sill seal, then you could put the plywood on the sleepers. This would eat up precious floor/ceiling height in your case and dramatically decrease your in floor heating efficiency.
Tile is an excellent finish product over concrete but it could effect the efficiency of your in floor heating, especially if you use a thick Mexican tile.

Stained concrete is a wonderful product, looks nice, easy to clean, durable and environmentally friendly and in your case, maintains the ceiling height.

If I were going to place in a wood floor, then I would try finding used planks from an earlier estate. Used wood will typically sound more organic and less shrill. And I totally agree with not putting the flooring directly over the concrete, meaning without some sort of a barrier.

Cork sheet that's 1/4 to 1/2 inch in thickness will be comfortable to walk on and it will provide an acoustic barrier. Any hard surface flooring like tile or concrete will cause sound waves to ricochet. This will also be a problem if the wood flooring is placed directly on top of concrete. As a hypothesis, I'm referring to decoupling the cement floor from the wood flooring above it, while allowing the acoustic presence of the wood to resonate. You definitely don't want to soundproof your floor or anything else, as this will totally kill your sound. However placing rugs on top of wood can stabilize acoustics without killing sonic presence.
IMHO

I had radiant floor heating in my house in Germany and the specifically chose tile flooring for the music room. The radiant floor heating is much more efficient with tile and wood. I treated the area in front of the speakers with area carpets and used room treatment to tame any reflections.

Fast forward to my return to the states a 1 1/2 ago, we built another home, except I chose wooden floors this time and no radiant heat. It seams Europe and radiant heat are synonymous with house building, not here in the states. Anyway, I treated the floors with area carpets and added room treatment, measured the room and all is well in the music room. I used bamboo flooring, one of the hardest versions that is a click fit and floating version. I used the best Bellawood under floor barrier, which serves to shield moisture from seeping through and to provide a better fitment for the flooring to attach to the cement floor. With lots of equipment, heavy equipment at that, some 285 pounds (speakers) and turntable with 275 pounds of mass with the rack, and subs, and racks, and large couch, the floor does not vibrate nor does it resonate, it is affixed firmly to the ground. I highly recommend going either tile or bamboo (harder than most other woods) for your floor. That has been my experience.
Good luck,
Audioquest4life

Thanks for your replies......It seems the consensus is for a hard floor. I might just go with the concrete and then if i want something different later i could tile or even go with the bamboo. I love bamboo and have a grove at my other home but I've heard mixed reviews about the flooring. But in this case it would probably work just fine. I was doing some measuring today and it looks like I have only 8 ft of clearance before finishing the ceiling or the floor. I'll probably go with double sheet rock on the ceiling so the lees flooring the better.

"I treated the area in front of the speakers with area carpets and used room treatment to tame any reflections."

Catfishbob, This is what you will be facing with concrete, tile or hardwood floors. If you carpet the listening room floor you will eliminate spending a fortune on room treatment and you will be much happier with the sound. Walk into any room without carpet, clap your hands and listen to the echo. This is what you don't want in your listening room.