Springs are the best solution, for sure. The method mitch2 describes will certainly work. It is however a lot of work. I went through it and have some springs. You are welcome to them. For about what it will cost just to ship them you could get a set of Nobsound springs. These work just as well but a lot better because you don’t have to calculate anything just add or subtract springs as needed. The leftover springs can be used under other components. Easily the best value in bargain vibration control.
If you want a lot better Townshend Pods or Brackets are a lot more money but worth it. If what you really want is isolation then Nobsound. If you also want improved sound quality and are willing to pay for it then Townshend.
In between, the other stuff you are considering, costs a lot more but not any better than Nobsound. Only worth paying more if making the jump to Pods.
If you want a lot better Townshend Pods or Brackets are a lot more money but worth it. If what you really want is isolation then Nobsound. If you also want improved sound quality and are willing to pay for it then Townshend.
In between, the other stuff you are considering, costs a lot more but not any better than Nobsound. Only worth paying more if making the jump to Pods.