Hi and thank you - your advice is most welcome :).
I've been using the multi-case setup for some time already (at first it was supposed to be a 40hp FX rack!) and never encountered any issues (including noise). What I like about it is the "workflow" that naturally emerges - keeping you "focused" on the modules at hand (I typically use 2-4 cases running on 1-2 power sockets). By combining cases in different ways you discover some interesting possibilities.
Having said that, I thought quite a few times of moving to a Mantis case and may eventually end up doing it sooner or later. And I also use knurlies :).
I'm curious to hear your comments about the choice of modules (some of which I haven't yet bought, others that I may decide to sell). Just imagine it's all in one box :)
Cheers