Hey Ironsave, I moved the table behind the left Heresy and moved both speakers within 14" of the rear wall. Actually, they sounded less good there, so I moved them back to the original position. I DID notice an improvement by removing the table that was behind the left speaker, though. Moving the fake plant behind the sub did not make an apparent difference. So I will leave it there in the interests of maintaining an acceptable WAF.
On another note (pun intended), I got out my handy dandy Radio Shack sound pressure level meter this morning, placed it three feet in front of the left speaker, turned off the subwoofer, and played the warble tone map from the Stereophile Test CD #2. What it showed (among other things) was a bump in the bass relative to the other frequencies from 100 HZ down to 70 Hz. After this, sound pressure gradually decayed until it reached 20Hz Interestingly, the speaker did produce measurable and audible sound at 20Hz.
At any rate, I responded by adjusting the low pass roll-off on my sub from 80 Hz where it was to 70Hz, to account for the new information gained by this morning's experiment. The result is that the setup sound much less harsh that it did before adjustment. It seems possible that the fatigue I was experiencing was due to a bass hump around 80 Hz, reinforced by my subwoofer.
Andy