Hi, i have a home theater built in my living room, this is somewhat a middleground between living room and dedicated room, i live alone so i can do what i want with the room, but i still want it to look somewhat like a normal living space.

Background: only read if you need all the details.
i bought this house in 2021, and i didnt check the standing waves beforehand. the standing waves resulted in big problems around the 60Hz range, i contacted a pro-calibrator, and he fixed most of my problems by moving my couch further back away from the 60hz standing wave. we tried multiple locations for the subs, but the front 2 corners gave the best frequency response.
Dimensions:
Length: 8m39 ; 27.5 ft
Width: 4m04 ; 13.25 ft
Height: 2m63 ; 8.6 ft

Standing Waves:
the 60Hz problem is manageable if i put the MLP at 3.9m

Acoustic Treatment:
for now i have 5 DIY panels with Rockwool (Rocksono) on the left wall. (2,1m * 0,6m * 10cm) for a total of 6.3m² (68ft²)
i will add one panel on the right wall later, and maybe 2D diffusors on the first reflection point left and right.
System:
Denon x3800h
Focal Aria 906 + CC900
Focal Sib Surrounds
2 Monoprice Monolith 15"
Frequency response after calibration:

RT60:

above 25Hz it looks ok, i think i dont need much more absorption.
below 25Hz, its still quite high, is this the source of my problems?
The problem:
i cant get the bass to a level where i am pleased with the sound. either its drowning out everything, or i miss punch in the music.
i tried manually EQ'ing the Bass response in the Mult-EQ app, but it doesnt really help much.
it think the bass just lingers too long in the room, its sounds muddy or something, i dont know how to describe it.
has this to do with the standingwaves around 60Hz? or might it be the long RT of 24Hz and below.
Solutions:
1) Add Bass traps
- Which ones (Soffit, Tritraps, turbo Traps)
- How many (2,4,6 or more?)
- Where?
2) add 3rd sub (the Denon supports 4 seperate Subwoofers) (or maybe with a minidsp)
- in back corner or Next to the couch
- could this be a smaller sub like a PB1000 or an Arendal 1961?

more Pictures of the room:


