Just a quick thought -- since you are using subwoofers, have you run a frequency sweep with a good measurement mike? It is real easy to end up with too much subsonic info that is aggravated by room nodes and has little or nothing to do with the music itself.
Alternatively, consider a rumble filter to the line level feed to the subwoofer amp, like one from Harrison Labs which comes in 20 HZ and 30 HZ high-pass options with 12 dB/octave curves. At about $30 on Amazon, they'd make for an inexpensive experiment and are returnable if you don't like them.
Disregard if you've already checked out this angle...