Thanks guys. I think I was not as clear as I could have been. The sub will be on the carpet floor below the rack, not really on a shelf or touching the rack, on the space below but between the 2 L-shaped vertical supports for the rest of the rack. The components will be in the rack above the sub. Still too close ?

My alternative is to build shelving on wall behind and above.

Either way it is time for me to put the components on something other than the boxes they came in.