The SPL module in REW does give the capability to specify the weighting, and REW in general is one of the most powerful programs an audiophile can have. I even use it for purely electronic measurements in my audio designs since it provides more information at-a-glance than my dedicated audio analyzer hardware/software.
There are also many SPL meter apps available for smart phones which are reasonably accurate and give the ability to specify weighting.
It's very good for that. Take the readings with a grain of salt however because some measurement 'irregularities' matter, and some not so much. Strive for a baseline flat response, then depart from that at-will for maximum listening quality. "Flat" doesn't always equal "best sound" - in fact it usually doesn't. Still, a baseline of flat is valuable as a known starting point.
