I have cutting boards that are exactly that thickness.
Does the amp sound better when it is overheated? Maybe you discovered a secret. I'm going to go cover all of my components with cloth and cutting boards to see if the imaging gets happier and more 4-D.
Your system even with the overheating modification is still incomplete. You have no turntable! How can a person be an actual audiophile and not hear the obvious superiority of analogue? Baffles the mind.