Room that long, I would try bringing the speakers out a lot more. Move the chair back. Leave the rack, or maybe move it further back even. You might also try them along the long wall. If you can. Main thing is to increase distance from reflections, especially first side, which we do best with distance.
You’ve got all these panels, so move them around listening for differences. One difference is bass reinforcement. Speakers closer to walls yields more bass, but tends to be uneven. Further away tends to be more lean and even. Where you sit matters too so every time you move speakers move and listen from different locations to find the most even sound.
The other big difference is imaging, sound stage width and depth. From where they are right now if you toe them in very slightly changing nothing else you will notice the stage is more focused and deeper.
So the usual process is move them around trying to find the even bass response, then fine tune for symmetry and toe in to get the focus and stage width and depth you want. This is all compromise. Its what you want. And it can change as you move things around and finish the room. But usually speaker location won’t change that much.
Also don’t worry too much about the low bass. This is something to fix later with a DBA. Those speakers once you get things dialed in and combined with a DBA will be flat-out awesome. Tekton. You have chosen well, grasshopper!
https://systems.audiogon.com/systems/8367
