My experience has been a tube pre-amp is least effected by footer/isolation than any other component including my SS amp. I know that makes no sense, but it is my experience. Having said that I use Aurios Pro, Neuance shelves, bubble wrap, Apollo rack, sandstone base sitting on Aurios pro's. See my vibration philosophy under "system."
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?