Where to use Isolation devices

I liked the effect of BDR cones under my SS preamp, but I found them even more
effective when used with Herbie's Grounding Bases.

Under the power amps, I use Herbie's Iso Cups. These are tube monoblock units,
so I would guess you stood to gain too if you used Iso Cups under your own
amplifier.

I tried myrtle blocks under my CDP and they helped, but Herbie helped even
more. Tenderfoot footers this time. Another thing that will help your CDP is
electrical isolation: a small isolation transformer. Also, a reasonably-priced
aftermarket power cord is worthwhile on a CDP. I use an Acoustic Zen El Niño.

I use Herbie;s Tenderfeet under everything I have except my Burson integrated. It has a thick and heavy case (6mm) that not only serves as the heat sink but is so effective at isolation that it makes the Tenderfeet a moot point, otherwise, I'd use them there as well.

I use Herbie's products under everything. The items used, placement and number vary by the piece of equipment.

I have tried uncusccesfully to "mix 'n match" manufacturers when it comes to isolation devices. In my opinion, I find it better to ID a manufacturer you like through some auditioning and then build your isolation approach with that manufacturer. Most I have spoken with, including Steve at Herbie's are very helpful.

For example, my TT rests on a Gingko isolation device that itself sits on a slightly larger 4" thik solid maple platform due to size issues: the foot print of my TT is larger than the top shelf of my Billy Bags equipment rack. Herbie was very helpful in working with me on products he does not even sell.

My two cents...

I use devices under everything and believe everything seems to benefit, including speakers. I use a range and don't believe myself, you need to use the same throughout.
Herbies products are always good value, I use the Isocups. I also have some Stillpoints and Black Ravioli, a UK product. Both are excellent and better than the Isocups, but a lot more expensive, even second hand. I have used or tried some brands I did'nt like, particularly HRS. In my system, they did'nt have much impact.
I am sure the way to go is to look out for second hand products on the Gon or other sites and just try them out.

The type of isolation/coupling to use, and where, and the "amount" of such is a matter of tuning (trial and error). I have never found it to be the case that more is necessarily better. It is possible to end up with a dry, sterile and harmonically bleached sound with too much of what is supposedly a good thing.

I have generally found the biggest effect to be under speakers. Often, the most commonly used device, the pointed spike (really a coupler, not an isolation device), is NOT the right approach over something like a suspended wood floor. In those instances, a platform with a foam type core to absorbs vibration is better than coupling through spikes (e.g., a Symposium Svelte shelf).

After speakers, I would address source components like turntables and CD players. These are sensitive components, but again, sometimes additional isolation is not what a system needs so it is a case of trying different things. I once helped with a trial of different shelves/devices under an Aero Capitole CD player that sounded surprisingly much worse with almost anything under it that is suppose to help with supression of vibration. The designer must have tuned his component for just what was needed (it came with something like Black Diamond cones for feet). My own CD player is somewhat immune to treatment--it doesn't sound that much different with special shelves, rollerblocks, etc.

In short, every system and component is different, so no single magic bullet works in all cases.