Marty,
Those tweaks that "work" (affect the sound) have a sonic signature. Most of the time, dampening vibration is desirable, particularly because it improves clarity and resolution. But, I am just warning that whether one likes the result is a matter of taste, system tuning and synergy. That is particularly the case with components like speakers and turntables. A turntable that effectively controls internally generated vibration and blocks external vibration may be described by some as quiet and well behaved, while others might characterize that same table as lifeless--it is a matter of taste and how each component interacts with or complements others.
Because CD players are mechanical devices, they generate a lot of vibration internally and are probably sensitive to external vibration so shelves or rollerblocks would normally be expected to have a substantial impact on the sound. More often than not, I would expect a positive effect, but, there is the possibility you won't like the effect.
I have also heard amps placed on Silent Running Audio (SRA)platforms. Those are quite effective too, but can be quite expensive. Like the HRS platforms, the SRA platforms are customized for each particular component (the weight and weight distribution of the component is factored into the design so that the dampening layers are optimally compressed).
Another caveat: It is easy to get caught up in certain obvious improvements, like greater clarity and resolution of detail, and end up losing something else that is harder to quantify or explicitly recognize ("musicality" or repose and grace). I've done this myself with certain tweaks. I wish it were the case that there is a defined formula or path for "improvement," but it really is not that simple.