I have a pair of Dynaudio Focus 140's on Dyn's Stand 4 stands.... I have both tubes filled full with sand will the bass be fuller if less sand is used.From my experiments with sand and lead filling the steel uprights of Sound-Lab U-1's, I'm certain the bass will be altered.
For better or worse is difficult to guess, the end result will be a combination of interactions between the stand, the floor, the speakers and even the footers used with the stand.
I would guess the bass will be more controlled with the sand, especially if you use spiked feet. Will that be perceived as better bass? You will likely have to experiment to find out.