Getting a sub off the floor is something Harvy "Gizmo" used to recommend. Thei is easy for a downfiring sub, just turn it over so it fires upward and put a board with something heavy on top. A little bit harder for a forward firing sub; you need a platform like this one. But I bet it would be better yet if you could raise it higher than that, say 1-2 feet off the ground.
This could definitely help with regular speakers by getting them off the resonating wooden floor. Well worth a shot, as long as your speakers remain fairly rigid while on it and not jingly and swaying. Remember a speaker is a mechanical device - the cones move, but the box should remain rigidely in place, otherwise your image will suffer.
Enjoy,
Bob