Effects of concrete as base for subs, speakers and potentially equipment

Hello, 

I am looking for any advice and experience from those that have used concrete as stands, racks, isolation. I have a friend who makes functional art pieces from concrete, coloured and designed to your liking and I was thinking of having some pieces made up for my equipment. I currently have everything on wood, but would like something more pleasing on the eye. My room is well dampened with wood floors. I am after any experience that you might have experimenting with concrete.

subwoofer on concrete slab. Currently have a T9x with a downward throwing passive radiator on a suspended wooden floor.  It needs removing from the floor and I was looking at concrete slabs. 
 

speakers on concrete slabs. Zu union 6 supreme again on suspension floor. They have isolation feet but they could do with lifting higher. I am considering using concrete for this. 
 

finally the equipment. Amp, dac, streamer. Currently on a cheap wooden cupboard with chopping boards underneath. Any experience of electronics on concrete.