I'm in the same boat with low back issues - but with L4&5 fused, 2 disc spacers etc.
FWIW I recently bought a BAT VK3500 to power my Harbeth 40.3 XD's. I'm really happy with it. It weighs 50lbs. I managed installing it without any difficulty - but it sits on top of the cabinet. Putting into a rack might be challenging though.