I find OP's question very difficult to answer. Different tweaks tend to result in improvements in different areas in sound quality. Some add a little more bass - my experience with good power cords, or give wider detail- my experience with cartridge, etc., etc. It really depends what specific deficiency in sound you're trying to alleviate. As for tube rolling, I have no experience in that space but I'm sure the same basic principles apply.
What to upgrade next?
If you wanted to make an upgrade which would be the next most noticeable improvement.
1: Power Cord (currently just stock cord)
2: Power tubes (currently JJ's 2 each 300b)
3: Cartridge (currently running Denon 103R)
My system consists of Audion Silver Night Special Edition 300b integrated, Acoustic Solid TT, Zu Soul Superfly speakers with Mission cables.
Rick
1: Power Cord (currently just stock cord)
2: Power tubes (currently JJ's 2 each 300b)
3: Cartridge (currently running Denon 103R)
My system consists of Audion Silver Night Special Edition 300b integrated, Acoustic Solid TT, Zu Soul Superfly speakers with Mission cables.
Rick