Which component(s) benifit the most from isolation?

Spikes couple directly to the floor.  Energy can go to the floor as well as come back.

I use speaker isolation springs. Mainly because they were $30 a set. I have Herbies under everything else.

Anything with moving parts.  Based on your list, CD player is next

@aewarren ”Your next-door neighbor’s speakers”

Brillient answer💡

Always great to think literally outside of the box.

Stack Audio Auva's under Wilsons, REL's, ARC preamp.

Nordost Sort Cone under dac and amp.

Iso acoustics under Aurender.

All rack hardware on 3 inch maple slabs, also on rubber pad interfaces to Adonna rack. Inexpensive in the grand scheme.

The listener..