What are the best Room Accustic Treaments members have found?

Primacoustic out of Canada is the real deal. As a division of Radial Engineering it's the same product that is used in professional recording studios. They have also standardized on colors, shapes, sizes and thicknesses so they can mass produce keeping prices low and product available for immediate delivery.

I believe also unique to Primacoustic is a paintable or printable panel. You can match or accent room color or have images reproduced by commercial printers using a big flatbed inkjet printer. 

I agree with the other poster about panel thickness and the laws of physics. A 2" thick engineered fiberglass panel is going to absorb effectivly down to about 100 Hz. The absorption of a 1" thick panel will not... A 1" thick panel works best as a scatter block on the live wall of a listening room (in an Abbey Roads style recording studio.) In a live wall - dead wall panel arrangement the speakers are on the dead wall. The scatter blocks on the live wall are a way to absorb excessive tweeter energy. In the live wall - dead wall arrangement the 2" thick panels are concentrated in the front half or 2/3 forward end of the room.

For control of standing waves typical to most rooms you'll need bass traps. Primacoustic has these as well and reccomended corner placement of the traps for best effect. The surface are of the traps should be calculated as part of the total treatment as discussed below.

There is such a thing as perfect placement. But the single biggest factor is having enough treatment to achieve your acoustic goals. This means having somewhere between 12% and 25% of the total surface area of the walls treated (not ceiling or floor surface area but walls only though paneling can be mounted on the ceiling if wall placement is not possible) depending on how "hard" or reflective your room is. Again, perfect placement is great but having enough treatment is the key and will get you 90% of the way to your goal. And that is good news because sometimes windows, doors and partner acceptance factors get in the way of perfect placement.

The nice thing about Primacoustic is that it's scaleable so that you can dial in your room. For instance, 15% not enough? Take it to 20%... Primacoustic reccomends changing  treatment in 5% increments as you'll unlikey hear smaller increments. (The tipping point is 5% with the big tipping point at 10%.) This way you can dial in your room the way you dial in your equipment rig with cables and amps.

Good luck with your acoustic goals.

+1 for avoiding a foam solution. It does not work evenly over all frequencies and is also a fire hazard. The best engineered panels are made of 6lb per cubic foot fiberglass. The way they work is that the acoustic energy hits the fiberglass causing the fibers to vibrate. The fibers vibrating against the air causes friction with the air turning the acoustic energy into heat... Something like a millionth of a degree or less... 

Fiberglass panels typically keep their shape with an acoustically transparent covering and a resin frame. 

Acoustic diffusers work great for diffusing the sound but do little to absorb excessive acoustic energy in a room. Furniture, rugs and carpeting can help absorb excessive acoustic energy in a room. But the problem is how much and what frequencies. Well engineered acoustic panels can help control a room in equal increments. Have a softDr room? Try 15% treatment. Have a hard room? Try more treatment but keep it to a max of 30% or risk making the room dead or dark... Unless, of course, dead or dark is your purpose or pleasure. Forensic labs might use a 50% treatment of 2" panels.