Which cone's or platforms have helped?

"The best cone material" is the material that works best for you in your own setup. Too numerous variables determine the optimum approach; the only way to find out is via experimentation. Even the specific placement of the cones certainly has a very noticable effect. I haven't played around with the DH placement tricks yet, but I suspect that even if some improvement is realized, I'll not be keeping them. They sound so slow & sluggish; dynamics & PRaT have all but vanished.
Gold plated brass was once recommended to me by a knowlegable dealer (who didn't even sell the cones which he suggested would be the best) & sure enough when I installed them under my speakers, the results were certainly amazing. This is not to say that some other material or product might not work even better; I am pleased with my results so far, so I haven't tried anything else (yet) although I probably will experiment further.
Going back to the CD player, brass has done well for me in my digital stack (see the above post) but titanium works even better. Black Diamond, a carbon fiber composition, falls somewhere in between brass & ceramic, which is to say that they were better than nothing but still not very impressive, in THIS system. Your mileage WILL vary.
Mr. Chichiuno has just sent me the Nordost titanium Pulsar Points to audition; I'll be trying them out next. Pulsar's are also available in aluminum at far less cost, so that might be interesting too. My VPI MK4 turntable has stock aluminum cones & they seem to work well enough, but again I haven't experimented in that regard. I've also seen wooden cones, & stainless steel is also available. It all depends upon the specific application & setup. Just as in cabling, there is no single "right answer". Sure do wish it was that easy... but half the fun is getting there.

Hey Bob, please let me know how the Nordost work out.
J.D.

I just read about a tweak using Styrofoam instead of platforms or cones, so I tried a solid block of 3" thick Styrofoam the exact size of my CDP and DAC (preamp and amp also).

I placed each component on it's block and the clarity increased dramatically. Passages that were entirely unintelligible, I can now understand every word clearly. The difference was hard to believe.

Try it, its cheap. If it doesn't work for you try something else. But don't be surprised if the results are as good as the most expensive options.

Fiddler, if I go to local Home Depot I can buy various sheets of foam insulation that have different densities and thermal properties. Do you have a more detailed description of type of foam you used....color, density etc. Some are quite dense/stiff and some are much softer.

What were you previously using under gear? Are component feet resting on foam, or just underside of case?

I can add this to JD's bubble pack tweak and get it all with one trip to Home Depot, heh heh.

Trip to home depot at lunch shows that 4x8 sheets of polystyrene foam (for insullation) are two basic types:
-white foam, less dense softer foam
-pink foam, rigid dense foam

Got a sheet of the 1.5" pink foam @$13, thickness available are 1/2, 1, 1.5 inch (no 3" foam) The pink foam is preferred I believe, if you check the foam inside Nueance or
Symposium platforms it is closer to pink foam density. Cut some bricks 8 inch x 4 inch with razor knife to position under gear and avoid feet or any vents which must remain clear. The 1.5 thickness is good because it easliy clears existing feet without raising too much (I could double up bricks for 3" height)

I am happy with existing brass cones and bearings, but this is a cheap, easy thing to try for reference, although will not win any interior design awards.