Anyone try stuffing their ports?

There is still some energy transfer even with the port being filled (not sealed). It has more to do with the room than the speaker.

If your bass is booming you can improve the sound by blocking the ports on bass reflex speakers. The only speakers I've needed to block the ports on had raw cotton fiber in them (PSB Stratus). I tried the foam from an equipment box I had but it did not give the result I wanted. I looked around but could not find any raw cotton fiber so I went to a fabric store and bought some pillow stuffing fiber which worked very well. Hope this helps. Happy listening.

You have'nt included a full system picture but it appears that your subs are to the outside of your speakers. One tweak that might make a difference is to put your subs inside the left/right speaker position and the exact distance from the listening position.