I used to use REW, but have had issues getting the sound card setup, using the REW interface is not exactly for newbies, and the SPL meter is not really a great Mic.
I recently came across this Frequency Response Plotter which seems to do an awesome job, and is very easy to use. Yes, I've been graphing again, and have some very impressive results. Oh yeah, and I've found that using my Mic that came with my Denon does a better job than my SPL meter as a mic, seems more accurate.