I just put a set of 3 small BDR Cones under my Parasound 2100 preamp. The BDRCs replaced a set of 4 Mapleshade IsoBlocks (those sandwich blocks w/ cork in the middle and rubber laminate top & botttom).
The BDRCs improved dynamics and clarity. Also, reduced that "shrill CD sound" (that's what I call it) on my reference recording with said sound ("Skin" by Beth Hart).
I was lucky to get these used on Audiogon for $38 including shipping.