Auralex sub-dude isolation platforms for sub woofers can also be used for speakers. I use them for my B&W803 diamonds. On hand I believe they are about $60.00 a piece. My 803's came with spikes which I use on the front of the speakers which sit on the isolation platforms.
A noticeable difference compared to them being on a cement floor even though the room is carpeted.
Thought this might help...just another idea in the mix.