The neo 1x12 cabs weigh about 34 pounds each, but bear in mind you would be moving 34 pounds twice instead of 50 pounds once on each trip. This is why I personally have gravitated towards single cab solutions, even if the weight per piece is bit higher.
That said, I have a friend with chronic fatigue syndrome so I understand what you're dealing with. If you don't have to rush to load-in/out at your typical gigs or can just toss them on a handtruck/cart, you would be moving less weight per lift. In fact, even you don't replace your 2x12 with a pair of 1x12 cabs, get a folding hand truck (if you don't already have one) or a cart like a Rock 'n Roller. The carts are nice because you don't have to balance them and your stuff is already 8"-10" higher off the ground when it comes time to load the car (less bending to pick them up).
Side note: You could set the pair of 1x12 cabs on their side to make a tall and narrow vertical stack, which could be better for monitoring purposes compared to a 2x12 on the floor (which is why I use stand with my 1x15 cab, for example). If you're running a rack width head as opposed to a smaller class D head, though, you would have a precariously balanced "T" shaped rig!