Have been putting in some thought to next set of 211 tubes, two years into my current quad, a third lot of 40s GEs.
Complicated both by my amps not being self biasing (I'd rather an engineer who knows what he's doing takes the risk with 1000V potentials), and the fact that there are no free trials or money back on tube purchases that don't work out sonically.
From £2k for AN 4242 and Psvane Acme, to £3.5k for Mayer Elrog 211, to £6k for Mayer Elrog 4242, to £8k for NOS Amperex and £8-14k for NOS Telefunken RS237s, this is a HELL of a crapshoot to get wrong.
Especially because I genuinely can't fault the SQ of my GEs.
So, as I scour the web to get any reliable data points, I find an interesting comment on Steve Hoffman Forums.
Someone has a Kondo Ongaku, known to be voiced around the GE 211, sounds great with them.
He also has an AN Jinpro, voiced around the AN 4242s, again sounds great.
But switch the tubes between these amps, and SQ suffers...in both.
And despite me not being able to prove it (Nat amps have so little about their engineering online, the company doesn't respond to questions), I'm sure my dealer said my SE2SEs are voiced around the GEs, and it would be a crapshoot to go beyond them, even for tubes that ostensibly are sonically superior, the Mayer Elrog 4242s, Amperex and Teles.
Better the devil you know makes sense, but wishful thinking in the high end can be the death of you...may be the reason I put to bed any fantasies of moving past GEs to "better" 211s.