Good uses for a sound pressure meter?

I bought the $50 Radio Shack digital meter to help with Sub integration using the Stereophile/Chesky test CD. Can't say I was that impressed with the resulting setup and just adjusted by ear. One thing I did notice was this. In the test for "spurious resonance" it starts with high frequency and progresses to low. When I heard fairly dramatic volume drops in certain middle freq. ranges I assumed it was the speakers but when I set up the meter and recorded the db levels there was no drops of significance during those parts . This makes me think that I 'm the one with a crummy frequency response. Comments? Also, if you have any other good ideas for SPM use, let me know. Thanks.