Frreol,
While I have had better luck than you with the Gold Lion KT88 re-issues I have also had excellent luck with The Tungsol 6550 re-issues. I am currently running them in 3 amps a CA50 ARC, Antique Sound Labs MG SI 15DT(single ended) and a McIntosh MA2275 all (so far) without problem. I too use the GE 6550's as my reference (I am down to my last well used quad) and the Tungsol's are the closest tubes I have heard to the GE6550 sound. I probably have 700>1000 hours on the pair in the ASL amp without problems. The CA50 will be the acid test however as it is brutal on it's tubes. Currently I probably have about 100 hours on that quad. Good luck.
While I have had better luck than you with the Gold Lion KT88 re-issues I have also had excellent luck with The Tungsol 6550 re-issues. I am currently running them in 3 amps a CA50 ARC, Antique Sound Labs MG SI 15DT(single ended) and a McIntosh MA2275 all (so far) without problem. I too use the GE 6550's as my reference (I am down to my last well used quad) and the Tungsol's are the closest tubes I have heard to the GE6550 sound. I probably have 700>1000 hours on the pair in the ASL amp without problems. The CA50 will be the acid test however as it is brutal on it's tubes. Currently I probably have about 100 hours on that quad. Good luck.