Stillpoints

CD players or transports yes! - because they do a great job of draining off micro-vibrations from mechanical devices. Amps (even tube amps) I think not so much. Ditto turntables. I have mine under my Wadia transport, and incredible as the TEAC VRDS mechanism is, the Stillpoints enabled some very bad discs to track properly -- and that's the only evidence I have because I couldn't hear any improvements in sonics (doesn't mean there weren't any ;-)
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I have found the Stillpoints to work well under my ARC CD3 MKII. They produced the widest and clearest sound stage compared to an assortment of other approaches. The shrill sometimes found in piano recordings in the second octave above middle C were noticably smoothed. I have purchased another set to try under my TERES TT.

The Stillpoints are very effective. I use them under the aluminum shelf that my Galibier sits on. Probably a bit more effective than a sandbox and much easier to use. I've not used them anywhere else in my system so I can't say what else they may or may not benefit.

For my tube amp and the power supplies of my preamp and phonostage I prefer Series +2 rollerblocks to drain vibrations off of the transformers. These are another very effective vibration control product. The results I hear are increased micro-details and air around the instruments.

I'll second Stillpoints with risers beneath transports and cd players.

I have stillpoints products under all my components. I don't know what your budget is, but stillpoints cones and risers in comination with their component stands worked wonders under my CD player and preamp. I also found the component stands to very effective under my speakers. The cones and risers by themselves definitely produce benefits, but the combination of cones and risers with component stands was highly synergistic.