I have additional sound deadening material if I need to apply it but Iām not there yet.
That's probably a pretty good idea in terms of cost. I checked earlier when I made the comment to see what the price difference these days was, and IIRC a non-isolated 18U is ~$800 and an isolated 18U is ~$1800. They aren't putting anything like $1k of sound-absorbing material into the rack.

