Experiences with mass loading stands

I have been using a cheap pair of steel Atacama stands for my monitors for the past few weeks. They have a single fillable post which has been filled with sand. Well I got them setup to where they were sounding pretty good so I thought I'd "upgrade" to a more substantial stand and ordered the Target MR 4-post steel stands.

I wasn't expecting much except for an increase in aesthetic appeal but I was shocked to hear that they made a significant impact on the sound- for the worse. The airy highs, mids and tight bass were now all gone.

This unfilled stand is at least twice as heavy as the filled Atacama it replaced so I am a little confused as to what is contributing to the bad sound. Will mass loading this stand further push the sound in the wrong direction, or will it give me back everything that is missing? Yes, I know I can just try it and see, but because of the design filling these stands will be a major PITA that I want to avoid if I can!