Thank you John, I took my unit back to the local dealer, they had talked to ARC as well, KT88 is ok to used in VT100 MKII, not MKIII. Instead of replacing the resistor myself, I trust ARC more in their QA and listening test. I decided to go with MKIII update, hope I had made the right choice. BTW, I'm testing my quad matched Svetlana KT88 in a friend's tube tester, just want to make sure they are OK, since my new MKIII can't use them, I would like to sell them (less than 5 minutes used). Let me know if anyone is interested. Thanks again
