I had the big AMTs sitting on the cabinets for a while and the sound was better than average but not what I wanted. I started playing around with flavors of caps for the high pass and ordered some ball bearings while I was at it. The difference of the isolation was tremendous. Much more noticeable than the caps.
If I hadn't gotten them isolated I probably would still be beating myself up over caps or something.
To do this it takes between $10 to $15 per speaker for isolation. A pack of 4 of the feet for washing machines is around $5 (Amazon). 6 (1") ball bearings $9 (Amazon) and the concave chromed steel rounds are drawer pulls, I bought at Home Depot for around $2 ea if I remember correctly, that I cut the stems off with a reciprocating saw and a vise. The washing machine feet are the easiest to do. I have tried hard wood and hockey pucks. The drawer pulls on top are simply adhered to the bottom of the speaker with a bit of silicone.
It works better than sorbothane, spikes, or sorbothane in the washing machine feet. The size of the ball bearings doesn't seem to matter, I have tried 3 sizes. I just like the looks of the large ones.
Looking at pics of a lot of isolation devices ball bearing seems to be popular and probably expensive. Not these. I also bought some roller bearings that a large ball bearing is on top of a layer of small bearings and crimped over so everything stays in place. I think it they were 8/$14. I haven't tried them out yet but don't think they will work as well as what I built, simply because there are more hard parts involved. There isn't a way to absorb or pass on the vibrations either but they can be screwed on the bottom of a wooden cabinet, make moving it on a hard floor easy and probably help pass the vibrations into the floor from the small bit of the ball that actually touches the floor. Not as well as spikes, but probably fairly close.