JJ makes 3 affordable EL34 tube types. I had no idea what they would sound like so I bought some. I'm using a modded Reisong A-10, 6ax7 Russian driver tubes, the feedback resistance is 545K (though I intend on switching it to 620K).

The JJ EL34 seems to be the mainstay of guitar amps without getting into exotic (expensive) tubes. Predictably it has a very strong midrange rolling off on the top and bottom (highs and lows). No surprises here.

The JJ 6ca7 is an interesting sounding tube. Guitar amp reviewers call it "dark sounding". Lows and lower midrange are strong, it seems to roll off early (compared to the EL34), so the upper midrange and highs are not "missing", but they are not strong and easily lost in music with strong bass. If you are running a sub woofer it will get a workout.

The JJ KT77 is an audio listening tube. It's strong midrange is extended up and down from that of the EL34. Overall it is the best of the lot for "listening" without an agenda. Well worth the few dollars extra.

As always, your mileage may vary, remembering listening is different for everyone.