Yeah, with a restoration, it is mostly about making it work and sound relatively the same way, but with more modern bits. But do all this with safety in mind, I would consider an upgrade in resistors to be metallized or wire wound versus the carbon ones because of temperature drift and safety of it all. Putting NOS 50 year old possibly dried out electrolytics in there is probably a nice thought, but modern electroyltics with a higher temperature rating and voltage rating will clean up the sound (to a degree) and even out the circuit, but again is more about safety. Corroded sockets that can arc over, gassy or worn out tubes that are going to overrun, or crapped out transformers are also not a good thing to have either.
Most of these things listed up there are in the power line side of things, so the audio output side of things (keep the chokes and OPTs if they are still working), that is a whole different matter. If you can keep that as close to spec as possible will still preserve a lot of "that Quad II sound". If your amp has them, then you have to weigh the paper in oil caps versus a modern polyester cap. But again, safety first.
Modification is probably not a good idea if you want to sell it, but safety and updating it is a good idea.
Now that the cart is before the horse, let's decide on the horse; are you going to keep it or not?