do hang in there, lots of burn in required!
the ultimate upgrades do seem to be subtle but some tube and rectifier changes can be dramatic upgades.
for tube rolling tubes 1,2,4 and 5 affect non balanced inputs, just get two matched pairs of the same tube with the pairs plugging into 1,4 and 2, 5.
if you use balanced inputs ( highly recommended) then you need another matched pair for slots 3, 6.
tubes 7 and 8 are for the headphone amp.
i use 3 matched pairs of sylvania 6SN7 GTA from the 50s and the sound blows away the EH stock tubes. you can barely listen to them after experiencing the sylvanias.
also do upgrade the 5ar4 / gz34 rectifier to a nos mullard f32. you can find brands made by mullard for reasonable cost.
again, another dramatic upgrade, especially in transparency and dynamics.