I've owned a 302B and as I recall the tubing is similar. I've had a bit of experience with some of those tubes so I could make the following recommendations for retubing. Of the current production EL-34 tubes I've enjoyed the ElectroHarmonix (EH) and also the Svetlana's which I did use in the 302B. Either will sound much better than the Chinese tubes they come with, and both are reasonably priced. You may also seek out some JJ Tesla tubes for more $ - if you can find some old stock from the early 90's in the blue and yellow boxes give those a shot, they're great EL34's. For the 12AX7's go with NOS Tungsram's. Last time I looked Jon had some of these at The Tube Store. I have no experience with mods on Jolida gear. You may want to contact Underwood Audio who does do mods on Jolida and is located near the US Jolida headquarters. No idea what "cales/wire" might be...a typo perhaps(?)
Marco
Marco