Nobosound Springs

I just added Audiocrast Spring Speaker Isolation to the rubber version of the antivibration pads (blue ones).  I have my subwoofers stacked and separating the subs with  springs was a huge improvement.  The bass is tighter, deeper and can be louder with getting boomy.  I did notice that it reduces the slam so some songs aren't quite as much sheer fun but the overall sound improved.  For subwoofers they provide a great improvement / price ratio.

I had tried a few "cheaper" isolation type products from Amazon over the years, never buying them a 2nd time due to the fact I never noticed much of a difference. On a whim but mostly due to them being slightly on sale and returnable I tried the Iso Acoustic pucks between my bookshelf speakers and stands. I was definitely amazed by how much they improved sound quality. Immediately I noticed clearer voices, midrange, higher frequency's.. initially that is what I noticed instead of the lower frequency's that most people rave on about.  The freaky part was now I could turn the volume up higher than before without losing any focus or it becoming shouty. Being able to turn the knob further helped reinforce that the improvements were not all in my head.

So while I had avoided the more expensive isolation products for the longest time due to their price and my doubts,  it turned out to be one of the cheapest upgrades I've made that had a significant positive effect on sound quality. I knew I had a "little" resonance coming from between the speaker and stand but had no idea how detrimental it was to the overall sound. The pucks made me such a believer that I ended up buying the mini ones and putting them under everything. How much of a difference that made I really don't know, can't tell a difference. 

I am not affiliated with this or any product/manufacturer. 

@mattw73 - I found the same with the volume. I was at 3 o'clock, can easily add 10-20% now and the SQ remains the same - no blurriness or shouting....

An update. I only had 4 Nobsounds - which I put under my turntable. For my Reference 3A de Capo monitors, I used four classic brass isolation cones for each speaker (something like these) and those, coupled with the Nobsounds, really opened up the sound!