Just to be clear - I was definitely not being critical of miro's setup, I figured he had done his due diligence and the materials he has under his monitors is vastly superior and more stable than the cheap bookshelves mine sit atop.
No problem, I understood that.
I m using a military sleeping bag pad. Its a very dense closed cell foam, almost like a medium hard rubber, you can pick it up at any surplus/ camping store.
You can lay it out on rocks and with your sleeping bag on top sleep comfortably. I also use it for a mat when crawling under my car.
Cut up for speakers it's outstanding. I noticed a definate improvement.
I tried the yoga mat thing, it's not bad, but this stuff is great.