That is completely contrary to my experience – the only amp I've tried this with was a Naim 32.5 and it sounds noticeably different to my ears with the case off.

You need to loose those ferrous Sound Org stands and then you will start to hear these things

I'm not saying it is mission critical, there is much great hi-fi with ferrous casing (Leaks, Quad IIs, your Accuphase etc) but the phenomenon Richard describes certainly exists. I've heard it.

Tony.