Start with Herbies Tube Damping Rings if there is space for them. This will help quell microphonics that otherwise might be picked up from the transformer. Then you might want to fix some sound dampening material to the chassis and/or cover to reduce resonances. Once you do all that, a set of Vibrapods or Vibrapod Cones and Isolators in combo should do the trick. They work great under my turntable and I use Vibrapods under all my electronic components.
I have a Jolida phono pre and line stage and use Herbies Tube Dampers inside and Vibrapod Isolators under the feet. I have no complaints. They definitely lower the noise floor.
