Thanks for the response. I have two subs that I have built myself. They are extremely large - they are 20" wide, 25" high and 30" deep. They weigh about 190 lbs each and are spiked. It is a vented design with a 12" woofer.
It is a massive effort just to move them around the room. That being said, I have experimented with different sub placements and trying to figure out the best position by using your initial steps. I have RoomEQWizard with a really nice corrected measurement mic. In all situations, the best results were having the two subs in the front corners and firing forward. If I had known better, I would have made these subs really tall and shallow because the overall frequency response became better as I pushed the subs closer to the front wall. The room is 11 feet wide, 17 feet long, 9 feet high. Room is completely sealed (no joining rooms via hallway, etc.).
Those soffit bass traps are long gone - sent back to GIK a couple years ago.
The response of the subs in deep bass is excellent. I pretty much have flat response down to 20Hz (really!!) and I can feel my clothes move on the low bass notes (it is definitely moving air!).
I understand the use of EQ in a system when done properly. I have worked with Dirac Live in my room and did not like the results at all. Even when I limited Dirac to under 150Hz, it still caused problems and bass impact wasn't the same. In my situation, I have a big dip (bass null) around 80 Hz which definitely reduces some of the impact of bass on certain music/movies. I don't think applying a +10/12 DB increase at the 80Hz area via an EQ is the right answer here. It is definitely a room node where I sit, so the possible options are the GIK flex-range-limiter bass trap or membrane bass trap. Or this Bag End E-Trap. Since you don't have any direct experience with it, I guess I'll just have to think about what direction I would go in next year. The GIK FRL and membrane traps are definitely cheaper, but they only absorb energy. The don't actively work on cancelling the bass frequencies by doing an inverted pressure wave (which could work better in sucking out the room nodes that cause those bass nulls/dips).