Don't be fooled. It can be just just as important to isolate solid state as tubes. In the case of the PWT and PWD both benefit from isolation treatment. I use Herbie's Tenderfeet with 2 Supersonic Stabilizers on top of each component. For proper results of any isolation system one needs to first locate the component where it sounds beat on the shelf if you are using one. Then experiment with footer placement, then component top weights. Besides the Herbie's products, I've used VPI Bricks, MpIngo Discs, Vibrapods and Vibracones, and cones of various makes and sizes. Some components, like my ARC Ref3 don't seem to need footers as the stock feet are good enough. Also if you can move your component racks so they are situated on the middle side walls, you'll hear a difference too. Vibrating components smear the sound and you can loose the subtle sonic details that can really make your system sound outstanding. Don't forget raising your cables offs the floor as well. I've found that each of these tweaks can improve the fidelity of a system and when they are all added up the difference can be profound.