From what I've read here and elsewhere, it seems that the size of the screen grid resistors have a significant effect on tone... less edgy, maybe? If I want to try 470-ohm screen grid resistors in a 6L6 amp that currently has 1k, I guess I need to double the power rating, right? What else do I need to be careful of? Does it make sense to first bias the tubes cold, then swap the resistors, then re-bias on powerup? Or just go for it? I plan to measure everything, but I guess I should be prepared to sacrifice the tubes if 470 turns out to be too low... any chance of damaging anything else? Thanks in advance.