I don't think anything on top is going to help much, it's the contact with the floor that seems to be the problem. I weigh 165 lbs. and when standing on it, it still moved. But that was before I had put the larger feet on it. But I don't want 100+ lbs. of lead on the top; it's already sort of an ugly critter. :-)
I'm starting to think that just bigger feet (more contact surface) of a tackier material would serve my purpose. Maybe the diameter of a typical amp or receiver's feet (2" or so), and an inch tall. Hmm, the feet on my old Polks are pretty beefy, maybe I could just steal them from there...
When I first starting working in the software industry, there was an IBM mainframe in the machine room by my office which was on the way out but still running a few applications. I had no dealings with that machine, but I knew the IBM repair folks because they were the same people that dealt with our RS/6000 machines. One day one of them pulled me in to the machine room to show me what happens when one of those old mainframe disks goes bad. Pieces of platter everywhere. :-)
