I can actually do the rehab myself. I just refurbished a SX-950 last month and 30 others in the last 7 years (even got good at diagnosing problems and fixing so that I had started to buy non working but good looking gear). All caps were replaced except the mains which test good and all the transistors were also replaced on the 950.
I've been finding that the transistors test out of spec even if they are working, especially the power transistors and the non working ones that I have purchased have all been transistor issues. It's all the brands with out of spec output transistors Yamaha's, Marantz's, Sansui's and Pioneer. I've been seeing gains of 10 or less on one or two of the output transistors. I'm guessing the small gold filament that connects the silicon to the contacts is thinning over time. So, if you're doing a refurbish then just change the outputs while they are still available.