This 60 Hz hum is driving me crazy

If your using tubes from the previous owner you have no idea how many hours they have on them.  I would say replace all the tubes and go from there.  I bet that solves your issue.  Others commented on a possible DC Offset issue but this usually manifests itself as a humming from transformers in your equipment and not a sound through the speakers as you describe.  Before you do anything...replace the tubes as that to me is the most obvious cause.  

@dill got the little $6 yellow tester (figured it is good to have regardless).  All outlets I have been using were OK.

Also moved the amp out of my mini man cave into the living room and plugged into another outlet....and the hum is still there!!!

I ordered the iFi DC blocker from Amazon to check that next.

My new speaker cables came in too, and no help.

If the DC Blocker fails, I will try replacing the tubes.  Does anyone recommend a solid place for both price and good tube reputation?  

For tubes I suggest Jim McShane or Brent Jessee. Both have websites and are good sources for tubes. Jim for good prices, Brent for the best.

You might have a ground issue inside the amp. I had one in my phono stage that was fixed by removing some paint from under the chassis ground wire. There was not enough bare metal exposed to make a good ground. The paint was acting like an insulator.

Thanks @dill! I will google their names.  There is no phono stage on mine but there is a ground mount on the back for a phone preamp.  To your point:

Talking to someone from Upscale service.  I mentioned that I lifted the ground but he still thinks its a ground loop.  He basically told me to Google it and try other things.  Haha

My phono stage is a separate, stand alone unit plugged into an integrated amp via interconnects and is about 1 1/2'away from the amp. The ground wire inside was insulated by the paint. I took off the ground wire, scraped the paint off and bingo, no more hum.