Edgecrusher:
After doing a lot of internet research on the differences between the current made Sovtek 6L6WXT+ and the EH 6L6GC, I wrote my tube supplier (a guy that has a lot of know how on glass, Dirk from TubeTown.net in Germany) and took the question to him after I noticed he did not sell the EH 6L6GC any more. He assured me the tubes were identical and that he did several tests (measuring, internal examination, tonal comparisson) to compare the Sovtek 6L6WXT+ and the EH 6L6GC and was totaly unable to find any differences at all between the two tubes except for the different label. Since the Sovtek 6L6WXT+ was the cheapest to buy (for him that is, don't know if it is always the case) for him, he stocked those and dropped the EH 6L6GC because he thinks it's crazy to pay more for the same tube with a different logo.
Another of my tube suppliers (Tonefactory.nl) gave me the same explanation after asking about the difference, he still does sell both the Sovtek 6L6WXT+ and the EH 6L6GC, where one is slightly higher priced then the other one, he leaves the decison with the customer and just clearly mentions these are the same tubes with the only difference the branding/logo.
It is of course not any proof because my tube suppliers say so (even if Dirk did pretty extensive testing on them to compare the two models), it was enough for me to firmly believe my suspicion on these being the same tubes.