Yeah... those PA speakers probably are not designed to deliver the lower octaves of bass. You got what you got... but, did you calibrate your sound card per the
REW Online Help File?
If not, your sound card may be pulling some of that low end down on the measurements. Also, what SPL/Mic are you using and are you applying correction files?
As far as room acoustics are concerned... probably some pics of your room posted in the Home Audio Acoustics forum would be a good start. Our guys are really good with acoustic treatment recommendations.