There are tons of isolation solutions for speakers, and you're going to get a lot of advice. But why not first try some high spikes and dig them into the carpet?
Speaker Isolation options for wood floor
My floor standing speakers are on carpet on a typical wood floor (second story). It seems that just using spikes would couple them to vibrations and "spring" of the floor. Therefore, are there any particular effective isolation methods being used (pads in combination with footers for example) that folks have found to be effective?