Why don't you try to cut everything below 50~55 hz (maybe up to 60hz) with reasonable slope on your master buss?
If this doesn't fix your problem, I don't see why smaller monitors would fix the problem.
Just don't forget to bypass it when bouncing and be advised that it will change the headroom.
Keep your money for acoustic treatment.
You know burny.. As unorthodox as that seems. I don't know why I never thought of that... but wouldn't just HP 50-55 to get a better image if i have shitty treatment then bypassing would muddle things up right? wouldn't it still be ineffective?
I am advising to do it as a permanent solution but just as a way to get a better grasp at what is causing the problem and how smaller monitors won't necessarily fix it.
The only real solutions are treatment and/or a more suitable room.