Cheap Isolation pads?

I do, the Auralex pads are pretty much standard gear. You have made heavy stands, which is the best isolator really. So, yes, tack on a pair of Auralex’s and you should be good to go.

They come with an insert so they sit flat, but without the insert they are angled lightly down, which is my preferred setup.

According to my own experience, there is some development that has gone into getting the right kind of foam. It’s not your run of the mill shop bought foam. Most reviews do claim (as I notice) a good decoupling. Combined with your heavy stands you should be doing well.

Again, try any cheap DIY option you like. I haven’t gone that route and am perfectly happy for the last couple of years with my homemade stands (sand-filled and wood) and the Auralex pads.