I had them at one point.They worked OK, but are not good at everything. Here's what I suggest.
Go to a sporting goods store (or Amazon.com) and buy some foam tennis balls. Cut them in half and try them under your components. Cheap squishy things.
Then buy some squash balls and try them. Cheap squishy roller things.
Then get some large steel ball bearings and try them. Cheap hard roller things.
Then get some hockey pucks. I think you may know what they are. Cheap hard things.
Find out which components like squishy, which like roller, which like hard and which like soft before spending money on anything more expensive. In my experience, tubes like soft & squishy. Turntables liked the squash balls. Transports, CD players and solid state prefer some version of hard isolation, some roller balls, others something else. And you can do it on the cheap to discover this. It's all trial and error anyway.