You can only make a small speaker so big, which is to say that a stand-mounted speaker is usually just that: small.
However some larger speakers, albeit mostly pro segment, aren’t shaped like towers - like ATC’s pro, active monitors SCM150 and 300 models - and so need stands. The Meyer Sound X-10’s (big speakers) needed short stands, if not flush mounted in the wall, to be at proper ear level. The S.P. Technology Timepiece speakers I owned +10 years ago were fairly bulky, weighed over 60 pounds per cab and needed taller stands to be lifted to ear level.
Obviously such speakers don’t qualify to be placed in the typical category of stand-mounted speakers, but being there are a range speakers that defy that category as stand-mounted items, why not just call their typical segment for what they are, i.e.: smaller speakers? So, why smaller speakers vs. bigger dittos?
I would say that if you’re high-passing your main speakers - be they small, medium or larger sized - then adding subs makes very good sense to find the better placement both for what the mains are supposed to do best, as well as the subs for their range of reproduction (I mean, you’re hovering on either side of the Schroeder frequency). Not to mention that you’re freeing up the mains from LF-signals, with all that entails of advantages. Ideally you need what’s essentially the same amps top to bottom, including subs, but that’s for another thread..
EDIT: actually, if your mains reach down into the 40Hz range you could experiment with running them full-range, and thus placing subs at a proper, minimum distance would add to the number of bass sources (mains + subs) for an effective DBA and smoother acoustical response. That’s two scenarios (vs. high-passed mains) that could be looked into and compared, and depending on the circumstances I guess could go either way with regard to preference here.
