Hi Acman3,
I placed an order for 8 mid-size Isopeds earlier this week for my speaker stands and unexpectedly received them yesterday. Since I was in 'new year eve mode', only had a few minutes of listening. Overall, I am getting incremental better bass (tight, extended and greater deliniation) large and deep soundstage and increase in low level details. I also noticed better integration between bass/mid-bass. I think my speaker spikes were robbing me a portion of the mid-bass.
I will eventually order additional units for my external speaker Xovers and monoblocks but honestly could stick with the actual configuration since the sound is so good :-). I don't know if your primary audio source has any vibration control device, but this is where I think the Isoped magic brings the best bang fot the buck. I would rate the Isoped as 7/10 when put below a source and 4/10 under the speaker. I'm not saying that they have no impact under the speakers, just saying that I had greater impact putting these under my DAC. I think that the law of diminishing returns starts to apply, once you get the majority of your 'bad vibes' corrected by the Isopeds.
The Isoped impact really shows up on well-recorded complex musical arrangements recordings (Lana Del Ray, Florence and the Machine, Dead Can Dance, large classical orchestras, etc.).
Again these are my preliminary comments and will try to move the Isopeds under my amps and Xovers to see the impact VS having them under the speakers.