Experience emilinating Ground Noise?

I need help gettig rid of the various noises that plague my McIntosh system through my loadspeakers; I have an MX130 pre-amp, and MC206 6 channel power amp, a McIntosh CD player, as well as a Panasonic DVD player recorder, and a cable box processor. I purchased a Monster HTS 5100 which did not get rid of the various buzzes that come through my speakers, but I did learn that when my voltage exceeds 120 the noises start. When it hits 125 volts it sounds like I'm being attacked by a plague of locusts, it's very noisy. Initially I had some luck getting rid of noise by eliminating the ground phugs, but this was only a temporary fix. Would love to hear from anyone with experence solving this sort of issue.