The 500 is definitely easy to rebuild... what I'd do differently in mine is skip the Jensen PIO caps (on the output tubes) for modern film-and-foils. I do like the way my amps sound, but I think it's easier to work with conventional caps, and I trust them more. The purple Sangamo caps on the phase splitter are PIOs (mine were oozing), and absolutely must go... those you might replace with Russian PIO if trying to keep as-original. But for the rest my vote would be Solen SM or CDE.
For resistors, I have used NOS carbon comps throughout. Most of the 2W resistors in my amps were drifted, and it was a very important step to replace them. I really went nuts with these, and purchased more than I needed of each type, then baked them in the oven at 150F for an hour. The driver plate load resistors in the 500a are paralleled 100k to make 50k combinations -- this is a great improvement over the 47k resistors in this position in the 500, and I would recommend doing it in yours. That way you can pick perfect combinations of 100k resistors to get exactly 50k load on each driver triode. Mine are matched within the limits of my multimeter's ability, and have not drifted in the 5 years since the rebuild.
For resistors, I have used NOS carbon comps throughout. Most of the 2W resistors in my amps were drifted, and it was a very important step to replace them. I really went nuts with these, and purchased more than I needed of each type, then baked them in the oven at 150F for an hour. The driver plate load resistors in the 500a are paralleled 100k to make 50k combinations -- this is a great improvement over the 47k resistors in this position in the 500, and I would recommend doing it in yours. That way you can pick perfect combinations of 100k resistors to get exactly 50k load on each driver triode. Mine are matched within the limits of my multimeter's ability, and have not drifted in the 5 years since the rebuild.
