Thank You for confirming why the carpet spikes are working so much better for me. I have carpet over concrete. My sound room is in the basement.
And again, just like I had mentioned to @ghdprentice , your config is different than what I had. You have granite (solid) on harwdood (solid). Mine was granite (solid) on carpet (soft/cushy). If I had hardwood below the granite, I would not remove the granite. Actually you have better options than me, to place the loudspeakers with Isoacoustics - directly on hardwood floors OR granite over hardwood. Good for you.