Well I've given up waiting until I get rid of the Sonos zones and gone ahead and put my rack-mount myServer into my equipment rack. Before I did it though I replaced the case fan with a 40mm Noctua one attached to a 3d-printed adapter. The original fan was a bit loud as it's about 4 feet from my ears and I work at home in my study every day. The Noctua fan is much quieter and fingers crossed hopefully pushes enough air to keep the pi4 cool.
And yes, my cable management and dusting skills leave a lot to be desired...
Andrew