I've made some speaker stands out of cinder blocks like in this article:

Velvetron

I've epoxied the cinder blocks together and epoxied the cinder blocks to a circular piece of wood. I did not add spikes like in the article. I have a couple of questions:

I have the stands currently on carpet. Do I need to use spikes at the base of the stand to de-couple them from the floor or is that not necessary?

I also need to add a platform to the top of the cinder blocks to rest the monitors on, what material should I be using? I see MDF mentioned in a lot of projects, should I use MDF epoxied to the cinder blocks and then some kind of foam between the MDF and speaker?

Appreciate the help! Let me know if I failed to include any information.