Zenith at the bottom of the brain stack for me. Bottom to top is Zenith/552/ND555/500. The brawn side already has five units 552PS/555PS/555PS/500PS/AV Amp.
To keep some balance between the two racks my dealer suggested the Zenith on the brain side as it’s a much smaller power supply that any of the Naim ones.
The above brain arrangement is forced by the size of the 500 head unit. I am however awaiting delivery of an Isoblue extension kit so I can move the 500 down and either the 552 or ND555 head unit to the top. This will make both racks (almost) the same height. The dealer has suggested I retain the Zenith at the bottom of the brain rack to try and help keep Burndies off the floor.