i've just purchased a pair of deck isolation platforms, they're made of 2 different types of foam woith mdf sandwiched in the middle, they were £20 each and they work perfectly, enough bass to shake a cupboard open and then spill ketchup, salt and vinegar all over the place and not even a hint of a rumble. the best thing is that the decks sit so solidly on them that you'd never know that they werent on the table directly. cracked the bass feedback problem 100%