I had a Rives designed level 3 room, which I ultimately ripped out and replaced with one designed by Matts Odemalm, of SMT, in Sweden. I also witnessed the same transformation of another local room (Rives Level 3 room to SMT). My experience was quite similar to those of Mes and Goatwuss noted above. I too spent a tremendous amount of time/money on a Rives design, yielding what I would classify as "unlistenable" results.
My advice - Select your room designer very carefully. Discuss issues such as broadband diffusion vs. absorption of mids/highs. Discuss actual volume, design, and placement of necessary bass traps and procedure for in-room tuning of traps. Ask who will be present to oversee the installation and tuning of acoustical treatment products. If possible, see and hear a room treated by the designer you are considering.
The products and design capabilities of SMT are now available directly in the US through Performance Acoustics Labs. Contact Mike Latvis of Harmonic Resolution Systems (HRS) to inquire.