I’m starting to build a decent rig this next couple of years after 40 years of lofi. We recently moved into a new home and my dedicated music listening and guitar playing room 12’ x 13.5’ x7’) is in the basement with a suspended ceiling. It currently has those thin architectural tiles like this.

The kind when you open the door quick enough they all move up.
I’m not concerned with HT type bass or sound going to the kitchen and laundry room above. I currently have my speakers out 4’ from the front wall (12.5’ wall) and 3’ from the side walls with my chair about 4.5’ from the speakers. This is where they sound best and the bass sounds tightest. So very nearfield.
As I start to buy new equipment, which will be very mid-fi to a lot of you ($3600 a year budget) I’m trying to think about room treatments for my squarish room. I’m keeping the suspended ceiling as I want/need access to water and gas lines there. Any suggestions on the ceiling that don’t involve major renovation?