The A 80 was not "portable" as yours. The "best" does not exist. It's highly subjective and depends on the listener's preference, you know. Those old Studers and Revoxes, like the G 36, are unique. They were ahead of its time. Some other people refers to the Studer machines as "the best mechanism" ever made, but don't like the sound so much and that's why the mastering engineers used to connect the head direct to external "tape preamps" like Mark Levinson did and some others.
Audiophiles are a difficult to pleased breed and represents a nice market for the upgrades and modifications. Some are really nice and you can notice real improvements, while others are simply BS. Anyway, if I like the sound of my deck "as is" I leave it alone. After all, it's up to the final user who needs to like what he/she hears.
I would like to have a machine like yours in that condition, though. It's a beauty. Congratulations!