I don't have anything even remotely close to Wally's technical skills; I'm just a player. My point is that, even beyond the technical analysis, the OP will have a subjective response to any sonic/auditory signal, as we all do. He asked what he could expect and while lots of folks have characterized what they feel the main difference between EL84 and 6V6 might be, there are so many variables in the process that it's next to impossible to estimate accurately what the OP might "expect". We'd like to be able to assess the difference with all other things being equal, but that's not easy to do, unless you want to fork over the pesos to buy an amp that can do that for you. I have my own opinions on how I respond to classic 6V6 v. EL84 equipped amps, but there's not enough consistency in those responses to come up with something useful for the OP - that's why I suggested he do some field research and come up with his own conclusions. What, it's a bad thing to go play through a bunch of different amps? Plus there are enough knobs to tweak on a Blues Jr, that along with a choice of guitar/pickups, you could probably make a 6V6 version sound like an EL 84. Just saying. ...in any event, I gig on a weekly basis with a Blues Jr. and seem to be part of a fairly small minority here that likes it. Come to think of it, at the gigs I play at, the only people who ask about the tubes are other guitar players.