I used to have some that I had filled with sand. I can't remember the brand anymore, but they were steel, painted black, and with the sand, were about 45 pounds each. They helped quite a bit with SQ in general.
When my basement got flooded, I lost my sub and sub amp, and rear surround speakers (they were on the floor, I had just put up some new paneling, and hadn't hung them yet). The stands survived the flood, but STUNK from then on, and nothing seemed to get rid of the stink. I finally gave them to a friend who had his uncle dip them insomething that took the paint and the stink off them, but afterwards, they got really rusty and looked horrible. I finally sold them to another friend who had them coated with Rhinoliner!
Why didn't I think of that?