I have completed a few upgrades. The driver tubes are now NOS Mullard CV 4024s with a RCA black plate in the center position. Jim McShane sent me a quad of reissue GL KT66s, which now have about 30 hours run time. I have replaced the Chinese rectifier with a Mullard GZ34 sourced from the auction site. Like Bob Latino, Jim McShane was a pleasure to deal with. The GL KT66s are a worthy upgrade from the Chinese EL34Bs. Glad to hear that my experience with this amp matches the other ST70s and ST120s that have been referenced here. I guess its time to upgrade the ICs!