How to physically move large heavy 100lb amplifiers easily (up and downstairs)

The easiest way is to invest in long speaker cables. 

My amp is 100Lbs.  The face has no protruding buttons etc and the back has 2 serious handles.  Once I got it to the bottom of the stairs, I stood on a stair step, swung it between my legs and up, one step at a time.  When I got to the top I did the same setting it down with each step along the carpeted floor.  Use your legs not you back.  If you don't have the handles this aint gonna happen.
Good luck.  -John

An elevator would do the trick. I think they run about 50k. Or perhaps some type of dumb waiter if the budget or space is limited.

Would something like this work?

https://www.amazon.com/Shoulder-Dolly-Moving-Straps-Efficiently/dp/B00022749Q/ref=sr_1_24?crid=1FWQP...

 Yeah, use the straps but invest in half a sheet of 3/4 inch plywood and make the "perfect platform" for the amp (trimming required).