Of the three choices you listed to me absolutely power tubes. You can do much better than JJ and the change in sound quality is dramatic and substantial with better tubes. That being said ohhwy61 has some good thoughts above on positioning which is indeed free!
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