Great news!
Congratulations on your listening room.
And you are in the basement. If you don't already have one, pour a really solid concrete floor slab. It will ground all your components: turntable if you have one, even CD player, certainly speakers. You will have an infinite mass below your sensitive kit. Well...if not infinite, then the mass of the Earth at least.
Then run dedicated power lines direct from the incoming supply and put in a bigger deeper earth post. This will save you a fortune in mains conditioners and silly expensive power cords.
Then set about your treatment of walls and ceiling others are advising you.
I have a room just like this and down there in the basement half your problems are solved from day one.