Do different speaker stands can really make a big sound improvement?

Your HARBETHs - like all HARBETHs - share an attribute requiring an “open” design and open construction speaker stand, instead of a “dulled-down” filled inert design cheap speaker stand. The latter make HARBETHs sound very flat, and comparatively dull ….. and these mass loaded heavy stands work opposite to how HARBETHs were originally designed to operate …… ergo: think TonTragers

- why?

- because the HARBETH speakers cabinet design is a bespoke and unique very thin-walled cabinet design, that resonates like the sound board on a Stradivarius violin, or a Steinway grand piano. HARBETH recommends an “open” and “airy” speaker stand design like the TT’s with their bespoke dimpled tonebeds and extended tenons to facilitate this .

I have the M30.2XD’s ….

NO! More malarkey from Harbeth!

The list of frivolous stuff that audiophiles convince themselves as making a meaningful sonic difference seems endless.  I don't understand how a flimsy stand would improve the sound of a speaker with a flimsy cabinet (Stradivarius, yeah right).  Use a solid stand, play with the footers if anything, and let your speakers sound how they sound.  Of course, a real audiophile would suspend them from the ceiling using springs.