Terrible Booms

The bass is fine . If you like the Proac sound I think the small Harbeths will give you many years of pleasure. 
IN BOCCA AL LUPO!

https://www.hifizine.com/2011/12/harbeth-p3esr/

Doesn't matter what speakers you use,or what footers or platforms.The bass waves are going to continue to cause the boom as they slam back and forth and up and down.To tame those waves you'll need to treat the front wall behind the speakers,especially the corners aggressively.8-10 inches of rockwool straddling the corners.Check GIK Acoustics site for more information and a free consultation.Here is a good site that explains room modes.http://www.sengpielaudio.com/calculator-roommodes.htm
Also adding two -four subwoofers will smooth those standing waves and room modes right out.Really!It's called "the swarm".
I have a less than optimal room myself and understanding and treating treating the room properly was a huge step forward.Adding two subs was another huge improvement,two more even better.If you really like your speakers do a little research first about acoustics and how to improve your space.

Thanks a lot-
I'll try everything you recommended

If your room acoustics cannot be improved, you need to use room correction.

Either use a preamp with this built in like Antimode or Anthem, or insert it between your pre and amp. I use miniDSP myself, but on the subwoofer, and because I already have all the room measurement gear I would need.


Looking at measurements, this is a low volume listening speaker, with a built in U/V shaped curve. It accentuates the treble and bass.  A room correction program may try to change both, so you'll want to get something you can control so you keep the original character of the speaker.

thank