Use the short wall, as mentioned. If you're not open to that. Try a few things to that should help regardless. Looks like you have tile floors. Place another rug (long and narrow) along the front wall where your speakers and amps rest...from wall to wall. Rugs/softening the room at the boundaries helps a ton.
That cleaned up the bass response in my room. I also bought a bigger central rug.
That cleaned up the bass response in my room. I also bought a bigger central rug.