Almost ALL the tubes from the 50's through the end sound really great. Course I think the modern production are pretty darn nice too. Not too many tubes I don't like And the Chinese are quick learners, so I'll bet it won't be long til their production will be better than Russians..I do like the older Russian Military tubes too. some really nice stuff out there...Tungstram and old Mullard signal tubes are about my favs, but for output tubes the Russian Mil tubes are pretty awesome. Still like the KT-120's too...just so much headroom in them. I don't think anyone makes an amp that will fully use their entire capabalities..