My experience with JJ tubes (except a rectifier that works fine) is that they're mediocre at best. A pair of JJ KT77s was so bad in my Dennis Had SEP amp that it put me off 77s altogether until I finally tried a pair of vastly superior new Gold Lions...JJ 6SN7GTBs were also pretty lame, but cheap enough I bought some out of curiosity anyway...they will sadly languish in my tube drawer as NOS GEs soldier on. Regarding the JJ GZ34S, it came with my Had amp originally but I prefer a 274B as it's larger and just looks cool.
Need Tubes
My Audio Research LS25 MK2 is in need of tubes. I was going to order a set from Audio Research but wanted to hear from you guys who may know of a better tube.