Also were you trying to integrate the sub by changing the cut-off frequency? This would seem logically to be the best way to do it, but it is not. It is much better to choose a frequency well below the lowest frequency of your speakers and turn the volume on the REL up slowly until it integrates. My Storm III is set at 38hz. My speakers are rated to 43hz. Many people use a wider gap, but my speakers are on the polite side in the bass. (A Storm III also goes deeper than a Stratus.)
I found a big improvement in the bass response with the Blue Circle BC62 power cords. They are on sale now for $125 on this site from Hello Simply Music. Well worth getting.
Have you also tried moving the speakers closer to the wall or corner?