That is a lovely looking room and system. I've struggled with various big speakers in a small room for more than a decade. And I've tried different things to tame the bass, and many of which as mentioned below, have worked for me :
1. Please try to analyze if you have a boom on certain tracks or at certain volume levels. This is really tricky to make out and needs a lot of listening and experimentation. In my case, I found that I had a boom when the bass went low, and higher volumes only made it worse. I accidentally tried an Audioquest Niagara 1200 to power my sources, and this removed the boom to a very large extent. I suspect that in my case, I had a 50hz hum on the power lines, which was probably causing that 50hz boom which has now been completely removed.
2. Adding isolation footers to speakers - I've experimented with both the Isoacoustics Gaia's as well as townshend speaker podiums. And found that both reduced the bass boom to a certain extent. I would strongly recommend trying the Isoacoustics Gaia III's under the monitor audio's.
3. Adding 6 inch deep "bass traps" of 4x2 feet on the wall behind the speakers. You just need to try with 2 traps. Each placed behind the speakers on the wall. These can be got from Gik or be made DIY. But Gik have the option of getting the panel made with printed art on top, which makes them look like pieces of art placed behind the speakers. Below would work great in your room. You have 3 options in that range, and I would suggest going with the "full range" option, which doesnt come with a range limiting baffle plate mounted on top.
The patented Monster Bass Trap with FlexRange Technology is our most effective panel measuring 7.5” thick, it absorbs maximum low end without over absorbing the high end.
www.gikacoustics.com
Iam aware that point 1 - power conditioning sounds ridiculous, but Iam just penning my own experiences. But I would strongly recommend trying just two GIK bass traps to start with and then add the Isoacoustics gaia footers to gain further. If both the above fail, then you can consider alternate speaker options, as Iam not a fan of using port bungs as I find they make the mid range sound congested and not free flowing anymore. All the best