Svetlana v. Genalex KT88 Tubes?

I have a pair of conrad-johnson Premier 8A monoblocks, each with 8 6550 tubes (plus six more small tubes). I have had two blow in the last week, and most are glowing very purple. They are currently Svetlana Winged C tubes. Someone has recommended Genalex KT88 tubes instead. Any opinions?

Thanks,

B.