you're never going to accurately get a comparison between speakers and headphones, as their principles of action and general characteristics prohibit such a thing
for example, while I feel my K701's to be tonally similar to Sonus Faber Guarneri Memento's, that does not mean the listening experience is remotely similar between the two, nor does it mean I find the Guarneri's to be the ideal dynamic loudspeaker
I would suggest trying to audition the speakers in consideration yourself, as someone else's opinion of a speaker (especially of a speaker) is quite invalid imho, with headphones this is true as well, but headphones will have nearly identical voicing (for example, my K701 will have almost identical voicing to a K701 owned by someone else, which means the overall "feeling" of the headphones is identical, and all thats changing is the human factor), while loudspeakers will vary with room size, treatment, and various other spatial considerations (quite dramatically, for example my parents have had the same pair of floorstanding loudspeakers for the last ~25 years, they've moved homes a few times in that period, and re-decorated a few times in each home, every time changing the overall presentation and signature of these speakers, they are fundamentally the same, but massively influenced by the room they're located in nonetheless)
based on this, you may feel an audition to be "quite worthless", which I would somewhat agree with (as you're dealing with the acoustics of wherever you audition them, sadly, unless you can manage an in-home audition (more on this later)), although you'll at least get a general feeling for yourself, of what they sound like
that can at least dictate "this is something I would like to further pursue" or "this is something I would not like to further pursue"
now, a home audition would alleviate this, as you would be able to hear them in your setting, with your room's acoustics, and your equipment, and know exactly how they sound for you, which gives you an image of "this is something I would like to own or use on a continuous basis" or "this is not something I would liek to own or use on a continuous basis"