Quatro Wood best feet

I maybe wrong

Granite will brighten and destroy your sound.Good luck though!!

You can try the Iso-Acoustics Gaia and if they don't sound any better send then back through Amazon. 

Start with the Vandersteen spike shoes, machined Aluminum cups the spike fit into
they have a felt pad to protect your tile.
they will also preserve the geometric relationship in the manual for tilt, ear height, distance to speaker.
iMO start there. Award winning sound possible that way.....

I did mentioned Iso-Acoustics Gaia to RV, and RV suggested put a 2 inch thick black granite on the floor and set the Quatro with its stock spikes on top will give much greater time improvement........may just stay with stock feet during speaker set up process.