I'm an Apple employee. My room is 17' deep, 12' wide 20' ceilings. 2 walls are metal, 2 are exposed insulation. No treatment (as of yet) but suprisingly dead sounding.
It looks likes a good option because it has a built in crossover at 50hz (adjustable) and my monitors are rated down to 49hz. Also, the bypass footswitch is sweet.