I would start with a few things.
Add bass traps along anything that resembles a corner near the front of the room.
Take off the rear absorption panels altogether and switch them with diffusion.
Now pull the couch 2 to 5 feet away from the wall. The more the better.
Pull the Left/Right front speakers out into the room. Preferably 2 to 3 feet in front of the screen. Toe them in so that the tweeter axis of each is aimed at the nearest shoulder at the listening spt.
Place two of the absorption panels you already have on the side walls at 1st reflection points. The other two should fit on the front wall, right beside the TV.
And if none of the above works... buy new damn speakers after an actual in-home audition. Maybe some Pioneer S2-EXs
Add diffusion panels in the ceiling at the first reflection points. Also add diffusion panels at reflection points where furthest speaker reflects off wall)