Need suggestions please! Electrical noise in my system and it's driving me crazy!

A TII 220 ground loop isolator put in between the cable line and cable box did it for me. Best $22 I ever spent. 
This was after checking grounding, electricians that found nothing and adding a hydra 8 into the system.  
Good luck. 

Thanks for all the suggestions everyone! Lots of great information and after reading everything I'm feeling like this is going to be more of a needle in the haystack than I thought. Problem isn't fixed yet. And it's weird because it's not steady. Some times it's worse that others and I'm going to start logging it all. When it rained really hard the other night it was noticeably worse. 

Some of the suggestions I've already eliminated, which number one... is equipment causing the noise, however my mono amps might be the culprit of some speaker buzz because I hadn't heard that until I added them to the system. I'm going to test that further. 

Second, I did have an electrician tighten all grounds and connections in both boxes, but I never checked all the outlets. That might take me forever so I might try some other things first. 

I do have internet coming in over Coax wire and then have CATV going into my OPPO 105D but I've unplugged it and plugged it back in with now change. I don't have cable, just internet, so only the OPPO is hooked up. 

An important thing to note is that I have two systems. I have a home theater room in one of my bedrooms and I have my two channel system set up in my living room. I'll list components at the bottom of this reply. 

One question that was asked, do I hear the humming and buzzing through the speakers or the equipment. It's both! My Furman Reference has a low audible hum and has a huge transformer (2 channel system), my Furman Elite has a loud audible hum (home theater). I have two amps for my home theater system and both have large transformers in them. They won't hum if they are hooked into the Furman but will hum if I have them plugged into the wall. With everything hooked up either through the Furman or not I still get buzzing through the speakers in both systems. I also get noise through my cheap garage stereo system and a small stereo I have in the basement in the work out room. 

Each system is on a different breaker but they are not dedicated breakers... unfortunately. 

****Now one thing to note is that is very different about my house is that the heating system is radiant heat floors throughout the entire house and garage using hot water and a commercial hot water heater to run it. I'm not sure if this would make a difference or not. Or could it have an effect on grounding. 

My 2 channel system:
Redwine Liliana mono amps converted with a digital power supply instead of the battery packs.
Rogue Audio Perseus Magnum Pre with Mullard tubes. 
Furman Reference conditioner
Toshiba SD-9200 (CD/DVD-Audio)
OPPO 105 (CD/SACD)
Magnepan 1.7i
All braided style interconnects and speaker cable from high end cable manufacturers. Upgraded power cords. 
**Tekton DIs are on the way! 

Home Theater:
OPPO 105D as the Blue Ray player and processor
Audio Refinement Muti5 and Multi2 amps
REL S2 Sub
Furman Elite conditioner
Same for cables as 2 channel, just a step down.
Polk Audio speakers
Samsung LED flat screen

Blindjim,

I'm going to go through your list of things first and see if any of it helps. I have some time this weekend to check some off. 

Thanks!

Two things to try:

1 - Turn off every other circuit in the home. You could have a dimmer somewhere that is putting DC on your line.

2 - Not sure about the exact Furman units you have, but try using the balanced outlets on the Reference model. Use power strips to extend them if necessary.

I've already turned all the circuits off in the house. I eve did it one by one to see if I could pinpoint the issue circuit. Only thing I gained by doing that is I made a diagram of which breaker is hooked up to what in the house. 

I'm not sure what you mean by number 2?