Simon Yorke recommends a 1 ton block of granite, i assume on a concrete floor. if that's not practical, a wall shelf onto brick or loadbearing wall is excellent, and personally i'd prefer that to active isolation devices like the vibraplane. That said, the Minus K is impressive indeed and a good solution if the table needs to be rack mounted. I'd still like the Minus K to sit on some mass and be decoupled though, so its not having to do too much work.
