What room treatment or treatments...

You need to go to Auralex.com. I am using in 13'x 15' room.

Bigger improvement than any component you will ever purchase.

Paul

I have a small room. Had Rives Audio do a "diy" design (wanted to build as many components as possible).

It includes:
RealTraps
Tuned resonators
Rigid 'glass (first reflection points & others)
RPG Diffractal
Ceiling diffracting grid (diy)

happy listening,

I'm using a number of DIY bass traps and absorbers based on a variety of Owens Corning 703/705 rigid fiberglass. I went DIY because I needed something that would exactly fit my needs, plus I wanted something that looked good in the room.

I currently have floor to ceiling bass traps in all four cornters, wall and ceiling absorbers at the first reflection points and I'm working on a couple of membrane-type bass traps and then a diffuser.

There's a lot of excellent information on the Room Acoustics forum (sponsored by Rives) over on AA plus Ethen Winers and Jon Risch's sites. If you have some basic woodworking/shop skills, you can get professional results and use all the extra money for more gear.