IMHO a better why to "isolate" a preamp is through transformer coupling. Electrical isolation IMO is more important than mechanical isolation. Ground currents in your ICs will generate noise, it's Ohm's Law. Even balanced ICs can have issues. Typical differential inputs have a high CMRR (common mode rejection ratio); but that's assuming perfectly equal source impedences. They seldom are: typical soures can have 10-20ohm imbalances. This can lower the CMRR of the reciever (amp) by 20db or more. Transformers have very high CM impedences and can handle source imbalances very well. High CMRR means your ICs won't be picking up any noise. I know transformers get a bad rap from some audiophiles; but you'd be surprised at how quiet and good a well designed transformer coupled system can sound.
preamp isolation
I have Symposium Rollerblocks with tungsten balls under my preamp. Yet, many of the thicker and stiffer IC's appear to be holding the component captive. I've added supports to my rack to help 'unweight' the pulling effect from the cables but I'm not sure how effective they are. Do the Rollerblocks still work properly with the cable resistance? Is there a better way? Thanks in advance.