As @petg60 has said, the footers can make a nice difference. The first tweak that got my attention were footers under my CDP. Cost $2. The tweak...Pumice Stone. It's used for pedicures. You can find it in the health & Beauty section of many stores. I was a skeptic about tweaks until then. Now I use my own DIY roller blocks. I can change the sound with the different materials used for the balls. Wood is my choice.
As to why NAD or someone else doesn't do the dynamat, it could be that they don't believe in it. Or the cost factor
As to why NAD or someone else doesn't do the dynamat, it could be that they don't believe in it. Or the cost factor