Re: Mesa Power Tubes
The STR-430s are Sovtec
The STR-454s are Svetlana
Though I heard they recently switched to a Chinese tube, but I don't know if that was for power or preamp tubes (they were using EHX for their preamp tubes).
Personally, I prefer the Svetlanas. Though I think I'll experiment with JJs next retube as lots seem to like them.
Robert - What pre tubes are you running?