I've found my granite slab insufficient by itself.
Although the imaging is super-solid, the bass went a bit muddy compared to the butcher block.
Despite weighing in at 150#, the slab still is affected by the subwoofer.
I've ordered up a different butcher block that's the same size as the granite slab and will be putting that on top.
I think one needs mass separated by something that flexes.
So I ordered this:
Double-B-Maple Isolation Platform
Was supposed to be here Friday - Late as is usual for UPS - will be here tomorrow.