300b vs. NOS mullard el34- both amps in push pull

Get some of the new KT77's. They are as good as the old Mullards if not better.
I thought they were in my Eastern Electric M520...better than XF1 with the big base.

Some of your answer will depend on your speaker load and your room. If you could answer that, along with how loud you listen and musical choices, we could make a more informed recommendation.

100db efficiency in a large room that is usually playing very loud complex music. I will eventually also try out a lower powered amp but for now 20 - 50 watt amps is what I'm going with.

I'm just wondering if the Mullard (xf2 not xf1 due to cost) has the beautiful midrange of a 300b in push pull if hypothetically both amps were the same. If not maybe I'll start considering buying a 300b p/p rather than buying those expensive Mullards for my el34 amp (I have come to the realization that I love a great midrange and will sacrifice other areas if I have to).

what kind of el34's are you using in your quickie now?
if you are into the distinctive el34 midrange sound, there are a few (cheaper) options to get very close to THE sound other than shelling out some chum for nos mullards; as Khaki8 has pointed out, there are some good KT77's and a few other current production 34's.

if you want to take advantage of your quickie's tube-rolling capacity and venture out to different tube sounds, there are some 7581A's, KT-88's and 90's, various 6L6's or even el84's using yellow jacket converters.

to my ears, many el 34's lack "air" and deep/wide bass in comparison to, say a nice set of tall-bottled RCA 6L6GC's or sparkly top of JAN 7581A's.
you might want to try out EL84's w/ yellow jackets; they have very good midrange (similar to 34's but a bit airier in the mids and have more brilliant treble, in general). plus el84's are cheap. i like groove tube's (selected JJ's)high number (6 and up) sets. these have more clean headroom than the lower numbered ones.

if it was my money i'd rahter save for a good 300b set amp than pp.
or even try some single-ended triode (MODE) versions of EL84's for a lot less $$.

Right now I am using NOS Tesla black base (supposedly not as good as earlier brown base) and like the sound much better than the EH KT88 I can run in them. It does not have that upper midrange hardness, has enough air, treble and soundstage for me.

Maybe I like the El34 is because the speakers I currently use are a crossoverless design which makes even the EL34 sound airy enough. Almost every other speaker I have heard sound more closed in and non-lifelike in comparison. However it does seem to be extremely revealing to amps which have any upper midrange hardness. That includes a couple of 845 amps I have had also in the past.

I also have a quad of Svetlana el34 which have the upper midrange hardness as well.

I have tried the almarro a205a (single ended el84) and another vintage el84 amp and they was pretty good except the top end was missing somewhat and not enough power for me. I have read from others the el84 is a little weak.

I have never tried a 6L6 but correct me if I am wrong that it is closer to the KT88 than the El34.

So in my continued search for the best midrange I'm thinking move up to the universally praised midrange of the NOS Mullard or start looking for a 300b amp.

yeah, el84's do lack power and headroom of the big bottles.
i can see why you want to try NOS Mullards, though many of the remaining nos tubes can be/are bottom of the barrel stuff and the performance can be disappointing.

it is hard to describe subtle tonal differences between several variants of 6L6's but i'd say 6L6GC variants in general have broader and airier sound than EL34's, and are different animals in terms of midrange presentation/tonal characteristics from El34's.

good luck w/ your search.