Go to an HVAC supplier and buy the rubber/cork/rubber blocks that are used under AC compressors. These are the same as the Mapleshade Isoblocks, but will cost you a lot less.
Tube Preamp Isolation
Currently using Vibrapod cone/isolater combo under my Music Reference RM5 MKIII. I've got it on a Billy Bags rack. I've got an Audio Research LS15 on the way and am wondering what you guys use (if anything) under your tube preamp?