Well... I'm considering it from a different set of factors. In 5.1 systems it has always (so I thought) preferable for the surround to be coming somewhat from above. I've personally never liked the effect of surrounds in a 5.1 system coming from ear level, and I have tried it. With Atmos...
Any decent stand probably won't have clamps or be adjustable. They also can be rather expensive. You might try the 36" (tallest) version of THESE. They're quite sturdy, and you can even fill two of the three columns with sand, if you want.