I have tried many many of these under my Tannoy speakers, ranging from the typical 5 cent coins all the way to expensive Harmonix footers. The best value for money and most effective turned out to be the "Linn Skeet". You can find it on ebay UK. Produced by Linn with real engineering behind it, not just typical tone control stuff that other tweak-accessories companies sell. Try it, you will thank yourself for saving a lot of time, effort and money. Costs only GBP 50.
Isolation disc for speaker spikes on wood floors.
Just did a little search, and it goes from pretty reasonable to quite expensive. Isoclean prices them as sets of 4, while others like Black Diamond and Symposium each. The BDR's are $30 each, but I need 8, so these things aren't cheap. The Isoclean's are $160/4, so they would run over $300. My sources are Music Direct, and Acoustic Sounds so far.