Chris, bricks don't work well under speakers and depending on where you
place them the sound goes from bad to worse. Lifting Tannoys 4" is
about ideal. the best solution I found is cans of food. Skinny ones work
better than fat ones. You got plenty of choices at your local supermarket,
contents don't matter as long as they're no taller than 4" and not too
wide.
david
PS Let us know how that works out for you!