I have some Amperex from old Hammond amps that break up really smooth, the American mades from the same sources seem a bit generic to me. I have some Tesla's that seem to be a bit mid strong (which I like a lot in some amps).
A lot of EL84 amps seem to drive the power tubes really hard, and in those cases the differences are much more subtle.
GE, RCA, Mullard, Polam, Telam, Telefunken, RFT- any of the old stuff is great IMO. These are the brands that I've tried but giving descriptions is really dependent upon the amp, guitar, preamp tubes, etc. They can be very pricey and finding matched pairs or quads can be tough. Check with KCA NOS Tubes, Doug's Tubes for availability and pricing. Ebay is a crap shoot.
Those are all great brands, but I'd certainly add Sylvanias (perhaps my fave) & philips/amperex. Most of the old stock tubes not only sound better to my ears, in my amps, but will last much longer.
that said, as much as I like vintage tubes, the JJ EL84 that I've tried sound really good, seem to last pretty well, & are dirt cheap. But maybe I've been lucky...
While others will disagree, but I no longer think that closely matched El84s is that important. After a very esteemed, older musician pointed out that most of the really good recordings of EL84 powered amps from yesteryear were made before anyone thought of tube matching (and hence were likely made with amps with unmatched tubes), I've experimented with slightly unmatched tubes--I really don't hear a big dif. between tightly matched & unmatched EL84s unless the mismatch is really gross.
That said, too, I've found that grossly mismatched EL84 (& 6973) produce some very harmonically interesting results. Sometimes, better than matched tubes (at least for me), including a lot of sag, complex harmonics, & very interesting (to me) amp distortion.
But I never assume that what I like is a prescription for others.
Enjoy the ride!
yeah Tubemonger has decent descriptions on the tonal aspect of tubes too but doesn't seem to have any tonal descriptions for the EL84's.