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

 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).

Would something like this work?

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

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.

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

The easiest way is to invest in long speaker cables. 

Need two, one under each arm.. or strapped, backpack style,  up the stairs I go.. Just have someone behind you, or tie a rope around your neck.. If you drop the amp, you'll want to jump..... pretty sure on that.

The box it came in strapped to a skit, and "skit it" up the steps, set on your butt and pull hand over hand, with a helper, tie the rope around their neck..  They won't mess up. Just once anyways..

If you don't have the ability. block and tackle, + Skit, is an easy way too...

OR like two people moving a person in a stretcher, two 2X4" 6-8 footers.

I took 375 pounders DOWN a spiral staircase, with a movers back strap. Took less than 10 minutes for the pair.. 30 minutes of prep... holding to rope rails with knots.. one step at a time. 12 steps a flat, 11 steps to the bottom.. 20" arms and 25" thigh, steroids do works. :-)

Regards

Or - - find someone with a strong back and a weak mind - ; )

Hand cart/dolly might make the most sense. One step at a time.