Avenger turtle-base STEEL stands do NOT get knocked over. They are heavy, but they are also very safe and stable. They can easily hold a softybox and 5-pound flash head without any need for a boom stand or boom arm. They are excellent in the wind and on uneven ground as well. A real bugger to carry, unless you have a small cart though.
Not sure if you know this, but if you are using "normal", light-weight aluminum lightstands at crowded events, one of the safest things to do is to ALWAYS clip or tape the light's power cord to the bottom, center of the stand, down near the floor. Because WHEN (not 'if", but "when") somebody's foot catches the cord as he walks, the light stand will simply scoot along the floor. If the cord runs from the ground, up, and then up to the flash head or monolight on the stand, if a person gets tangled in the cord and walks, then the pull tips the flash and stand OVER, from the top, where it's heavy, and the light falls down, and goes BOOM! (or tinnnnk...), and there goes a flashtube, and the reflector is often dented.
This is why there are cable-clips sold for the more-popular light stands...they allow you to "clip" the cable in very easily.
A second thing are caster-bases; these wheel sets are handy at preventing "fall down, go BOOM!" issues in case a person gets tangled with the cord.