LinLai WE 300B or the LinLai Global Elite Permaloy 300B tubes ?

@sns,
I honestly believe that you’d be happy with the Lanlai Elite 300b. In regard to tube testing I had my EML XLS tested last week. This pair was purchased new in early (JAN/FEB) 2013 and have been used heavily in my Coincident Frankenstein 300b SET.

@liquidsound, my friend has an Amplitrex tube tester.
Reference scale for transconductance/gm is 90-100= "test like new"
80-89 = "Great" per this particular machine.

My two EMLs tested 83 and 85 respectively. Impressive I thought after over 8 years of heavy usage. Lots of tube life remaining.  Not inexpensive tubes but they last quite a while and have superb sound quality. 
Charles

Indeed Charles, I own the 45's XLS, excellent quality and great sound

http://amplitrex.com/wp-content/uploads/2017/12/at1000_001-1-1024x384.jpg
I can vouch for this device’s ability to test a very broad variety of tube types.
Charles

Yep, that's the tube tester used by my source.

The Amplitrex is a terrific tester.  For my purposes, the best thing about it is that it is idiot proof.  You select the tube type to be tested from a menu, the machine tells you which socket to use, it warms up the tube and then begins the testing.  The testing is done at full power , which is the best way to detect weakness.  The tester displays real values, not just some arbitrary scale, and also shows the specified value for a new tube to compare the value.  The displayed values include emission, transconductance, and noise.  The machine also provides—“good,” “bad,” etc.— evaluations.  If you hook it up to your computer, it will also trace the tube.

I like my tester a lot.  There is no looking up and setting values on the tester, as is the case with something like the TV-7, so this cuts down on mistakes.  I’ve noticed that it is a hard grader—tubes that test extremely strong on a TV-7 may not grade as well with the Amplitrex.