lucaskite's did a wonderful job describing all these tubes. Thank you: I found this very helpful.
However, re: the Mullard EZ81s--it sounds like he may have gotten a bum pair. In fact, I'd rank the British-made Mullard EZ81s (often OEM Philips Miniwatt) as #2 or 3 on this list. Mine are really quite wonderful. Clean-sounding; expansive sound stage; dynamic; good imaging; well balanced; good speed for micro-details in timbre. Sweet treble.
The Blackburn D-Getter Mullard EZ80s (#5) have magical mids, as stated--but at a real cost in bass and treble. And the focused soundstage (rather than focused, I'd call it "vastly diminished") basically kills one of the best features of HD800/HD800Ss. Jack Woo's on record saying they're the best rectifier for the WA2--but I really disagree on that one.
As others have noted, RFT EZ80s should be added to the list--but they get more recommendations for the WA2 (in my opinion) than they deserve--but they're relatively inexpensive, which is an important virtue. Accounting for quality to expense ratio, they'd be very high on the list. They're great rectifiers except for that slight bump in the upper mids, which I find offputting.
Someone
here, when asked what the best EZ80 was, amusingly responded that the best EZ80 is an EZ81. I'm inclined to agree--top two for me are British-made Mullard EZ81s and, above that, British-made Brimar EZ81s (often OEM GE and Sylvania). The British-made Brimar EZ81s are revealing without being fatiguing. They're well balanced, with wonderful bass extension. The mids are luscious and rich. The imaging is complex and layered--holographic--and the soundstage is vast. They're really fast as well. So far, they're my gold standard for rectifiers.
But I've yet to try the Marconi/Osram U709s (EZ81s), which
some people swear is the best (but also very pricey and rare these days). Brimar EZ81s are difficult to find since they're highly sought after.
Kef Tesfaye at ValveTubes.com (in England) is a great source for difficult to find tubes--nobody better for British-made tubes.
Anyway, thanks again, lucaskite, for the wonderful guide.