Amplifier Hum, and placement.

I have a Simm Moon W-5, which just started humming, when I moved into my new house. I have a dedicated circut for the amp, and use a richard gray that is plugged into hospital grade outlets. after trouble shooting, I have determained that it is a mechanical hum. When I tightend the transformers, the bolt moved alot, and probably can be tightend a little more, can I damage the transformer by doing this? The hum is still present, but the pitch has changed. The other question is I have a friend in the headstone business, that is cutting me a piece of level granite to put my amp on, Good or Bad?
A headstone? Yikes!! My girlfriend is Chinese, and I believe that would be a no-no (hopefully you're not superstitious!). But seriously, I would e-mail Costa at Sim Audio before messing around with the W-5 (I think its, but check the site). He is very helpful- I own the Sim Attraction HT processor, and used to own the Eclipse CD player- they are generally quite good with customer service. Good luck, and great amp!
I once owned an older Classe DR-10 amp that had slight transformer hum. It was annoying between CD tracks but not loud enough to interfere while the music was playing. I sold the amp cheap and all of my recent gear has been "clean" with no transformer hum. I would contact your dealer or the manufacturer because high-end ($$) gear should not do this and you should not have to deal with silly tweaks to try to eliminate it. BTW, placing your amp on a surface to reduce microphonic pickup is probably a good idea but I don't think granite is necessarily a good choice just because its hard and heavy. You might want a good amp stand with spikes.