After a lot of thought, I'm going to go down the active isolation route, now that I've gone all-tube. This will mean 6 shelves in total, but will only be able to afford buying used. And I'm going to only do this as my last layer of upgrades - I'm going to first upgrade my passive Symposium Isis component rack and 2 floating Isis stands for my new monoblocks (cost of 5 layers of passive equivalent to 1(!) active layer), then a new i/c and power cord loom, and then upgraded 8kVA balanced power. There are just too many logistical issues to go active just now, and I'll get more VFM maximising current passive isolation/wiring/power which will still amount to less than 6 active shelves new. But I'm settled on the positives of active.
Attaboy!