Ayon Triton III — KT88 BTSX Tubes? Tube sources?

Can anyone explain what is different/better with the KT88 BTSX tubes that came with the current generation Ayon Audio "Triton III" integrated amp?

...Are those the best tubes for this amp?

Also, I simply can not find an alternative source for the stock KT88 BTSX tubes, I'm sure I will pay the maximum by approaching the dealer, but so far thats my only option for the BTSX tubes.

thanks!