What are the tonal differences between these and the foil and papers? Would they also change the dynamics of an amp being retro-fitted with them? The reason I ask is that I have a Traynor combo ('74ish) that is bone stock and it needs caps. I understand that this will change the amp some, but would the oil caps be worth the extra money to replace the old mustards? Purists please don't burn me at the stake for this! This is a player and not a museum piece. Thanks in advance y'all!