I only replaced the capacitors and the relay on the power supply board. I've seen Japanese websites where they replace the glass diodes (they call them dame diodes) with modern equivalents.
I found a lot of cold solder joints and just bad soldering altogether. If you compare the KA 7100 and the KA 9100, you notice that the 7100 boards used a more modern process than the 9100 (Probably since they made a lot more of the 7100) and the 7100 had perfect soldering. Some of the boards had an amazing amount of flux to be removed.
The preamp was a pain to disassemble and reassemble. I had to do it three times (lost the left channel because a wire came loose) and found that it was easier to remove if you disassembled the facia from left to right (can probably do this in my sleep now).
After recapping, cleaning switches and diagnosing the fault (I created) I will note that this is a great sounding amp for my Cornwall IIs and it's been in service since May (knocked the CA 2010 and AU 717 from rotation, maybe the 9900A will knock this one off once I set the bias). Phono section is very quiet, which is what I prefer (no coloration).