As to the Amps thing... if a single amp can't be lightweight, then maybe the components can be in separate boxes? so at least each box is smaller & can be carried against the body rather than having to lug all of it in one huge ungainly box.
...this is kind of what I suggested w/the Barbetta Sona 31c's - only 32lbs. (which is comparitively light) but way powerful, yet if you bring two of them, you have a nice stereo setup!
BTW -
If the Peavey amp is only 20lbs. yet you're having trouble moving/lifting that one, Laura - then you're in quite a jam, 'cause they only get heavier. Anything under 50lbs. is considered light in the world of live sound and amplification, believe it or not...
Maybe once your back sprain heals you can do some weightlifting to strengthen your upper body or something... sounds like you're a little person to begin with so I sympathize, as I am small too (5' 7", 155 lbs.) but I have to grin and bear it, 'cause I'm a man...!