Thanks all for the feedback. I did contact GIK for advice and they pretty much said buy traps...a lot of them
Bill, you motivated me to start taking some measurements which led to a long day of shuffling 4 subs around into what seemed like 3,000 positional and phase combinations. My two lesser subs are nearfield to the seating and I got some results across my seating positions that are making me very happy. Not more than a dB or 2 difference across my first row. All money seats!
These first graphs are smoothed 1/6 and were all taken at the same SPL but they are simply offset. I need to level adjust the subs a bit and these are raw graphs with no EQ, but those curves should EQ well for sure!
The three tracings are my left, middle, and right seating positions.
And of course there is the obligatory unsmoothed graphs. Sorry they're chopped off a bit. But the chopped one looks just like the unchopped ones. All peaks, no nulls which means they are VERY EQ-able.
A long day of moving subs, figured I would share the results
BTW, that's the best seat - to - seat variability I've ever achieved in my room.