Chris
I tried brass cones DIY, but had WAY better results with aurios types again DIY. Currently have under digital source the following combination: special polymer cones directly in contact with source chassis, supported on 3/16 steel plate treated with dampening material( silicone caulk ) cut aways for the cones resting spots, rolling ball underneath the steel plate. For the time being.
When my room is assembled ( moved recently and haven't finished unpacking the house goods yet so, stereo has to wait) I have the steel rolling bearings that support the plate placed on top of a MDF sandbox which has another steel plate on top.
Cumbersome but so far haven't been motivated to "mess" the nice sounds that come out of this contraption......
Have no rack. Every component seats on the floor on top of variations of the above combination. Floor is concrete in my case.
How long have you been using the Signal Cable IC. Do you expect improvements with more time ?