I thought our drivers were the same? I've got 4 PM752 drivers on a 500VA (I think) toroidal transformer. Maybe it's the big capacitors that cause it...

I think the surface should be conductive enough for an earth. Whether it's a good idea or not I'm not sure. I'd be inclined to say yes.

Good point about the dust. Any fans in there are going to blow in a lot of dust. I found about a 5mm layer of wood dust (and some metal swarf!) in my computer when I cleaned it out on Friday. Probably should have made sure the case side didn't keep falling off, but still...

Edit: didn't see your last post in time :(