The important requirements for a nearfield speaker stand is that it
isolates speaker vibes from the floor some way,
doesn't move around,
doesn't introduce any audible resonances, and
puts the speakers at an optimum height.
In order -
Isolating vibes - this could be done at floor level, using some sort of damped elastomer such as butyl rubber; good part about this is that it causes the weight of the stand to be included in the weight of the speaker - in this version the mass-spring-mass would be floor (first mass) butyl rubber (spring) and the entire weight of the stand, sand-fill, and speaker (which would be solidly attached to the stand in this case)
Isolation could also be done at the junction between speaker and stand - in this case you'd have the sand-filled stand (and part of the floor) as the first mass, then something like a MoPad or butyl pucks (the spring) between the stand and the speaker (the speaker being the second mass) -
The problem with this arrangement is that most speakers aren't heavy enough by themselves to properly compress a high duro material to at least 10% of its thickness - a lighter duro (spongier) material, while allowing proper compression, will allow speakers to rock at higher listening levels due to the force of the cones moving back and forth.
One way around this would be to place heavy steel plates on top of the speaker to increase the upper mass of the mass-spring-mass assembly - this would keep MSM resonance lower, keep rocking to a minimum, and still isolate speaker resonances from the rest of the room.
The reason this isolation is important is that sound travels faster through solids than it does through air; so if your speakers are solidly coupled thru the stands to the floor, and thru the floor to your desk, then it becomes possible for the desk to radiate the sound to your ears BEFORE it gets there thru the air - this scenario will cause smearing of higher frequencies thru phase differences, and just generally cause muddier sound.
doesn't move around - Having a solid stand and speaker helps this - if your "spring" is located between the floor and the stand, it needs to be pretty firm. This means that to achieve low resonant frequency (subaudible) you need pretty heavy stands and speakers in order to get at least 10% compression of the spring material.
The reason for this is that ANY spring, be it metal or rubber or whatever, is ONLY a spring when it is NOT at either end of its travel. Example - take a spring from a Hummer or a Mercedes sedan, and allow someone to hold one end of it and hit you in the face with the other end - after you regain consciousness, you'll probably agree that it wasn't very "springy" - this is because it's designed to hold a 6000 pound car (or at least 1/4 of it) so in a free state, until you load it with about 600 pounds it acts as a solid piece of steel. It's the same way with rubber or butyl or any elastomer that's used as a spring - until you get away from the two extremes of travel, the material acts as a solid. This precludes it from becoming your spring in this mass-spring-mass assembly.
So the solution to this is either use fairly stiff (like 60 durometer) rubber under your stands so they won't rock, or put your "spring" further up the column so the "rocking force"(speaker cone movement) can't cause things to move as easily. This would be where the springy material is between speaker and the top of the stand.
doesn't introduce any audible resonances
These can be caused by insecure interfaces between speaker and stand (no pad of any kind), not enough mass on either side of the spring material to keep MSM at sub-audible frequencies, or using a 4-point base on the stand without having some sort of adjustment to keep all 4 feet firmly in contact with the floor.
puts the speakers at an optimum height
This is covered in the Acoustics forum - basically, you don't want your speaker's woofer to be within about 6" from the center of your room height, measured NOT from any acoustic absorber but from the hard surfaces - see "are my speakers in a null" in the acoustics forum for more on this.
One simple (if inelegant) way to accomplish all this is to buy some hollow concrete blocks, stack them up to about a foot below half your ceiling height, put some MoPads on top, add your speakers, and generate a slow sweep signal into the speakers while listening for resonances. Rattles will be caused by lack of firm connection between two objects, louder frequencies will be caused by either room modes (see the thread in acoustics again) SBIR (Speaker Boundary Interference Response - similar to modes but caused by speaker placement relative to walls/floor/ceiling) or not enough mass on either side of the MoPads (or other rubber product)
