amathusiast I know you are weary of headphones, but I found using my BeyerDynamic Semi-open headphones to work really well. Being semi-open, you can still hear ambient background noise, like birds singing outside, or for better or worse your phone going off. I could never get monitor speakers to sound right with Pianoteq, although including a subwoofer really helped.
I have two open back headphones (Sennheiser HD558 and HD600). Then, out of the same concern about protect my hearing, I got a pair of studio monitors (JBL 306p Mk2). The studio monitors sound remarkably close to the headphones. They may lack a little bit in the bass, but their fidelity is markedly better than my semi-audiophile bookshelf speakers (Pioneer BS-21).
I do have a SPL meter and used it to verify the sound volume settings. I am no audiologist. However, the theory of speakers being less detrimental to hearing due to sound dispersion does not quite make sense to me. Our ears are sensing sound pressure/energy at the ear drum. They can't tell where the sound source is placed or how it arrived. The same energy at the ear drum (which we sense as the same volume) should cause the same harm to hearing, provided the frequency profile is the same. Therefore, even if we sit farther away from the speakers, they could be equally detrimental if we turn up the speaker volume so that they feel just as loud as what we hear from our headphone.
I suppose there could be convincing correlation between headphone wearers and impaired hearing. But that could just be caused by headphone wearer's higher tendency to turn the volume up - because headphones don't bother people surround you as much as the speakers. I remember reading about a rule of thumb that if you can't hear finger tapping on a desk surface while wearing headphones, your volume is too loud. In my experience, it is surprisingly easy to exceed that volume.
Back to SPL meter. I measured at my listening position (ears), with my settings, the sound pressure ranges from 65dB (p) to 85dB (ff). That in theory should be a safe range, especially considering we aren't playing ff all the time. One thing I did notice, because of the SPL meter, is I must be sure I turn off the on-board speaker of my Roland when using studio monitors. Having two sets of speakers firing at the same time greatly increases the sound pressure reading.