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

You people live in a world where neighborhood teenagers will help with menial tasks for $10 or $20?  Wow. 

When we get older, install one of those to transport our-self and equipment.

https://www.bruno.com/stair-lifts

If there was an Army Field Manual on it, it would say that Soldier B would grab the other handle and up the stairs the two of you would go.  The good sense civilian approach would, it seems, be similar.

Yes. This is ridiculous. Injuries are
difficult to get over once you're over 40. After 50 they can threaten to become permanently debilitating.

Well said!